The Android version of Zotero-Beta, Version 1.0.0-247 and 1.0.0-255, is not available.

I'm not sure what you mean by this.

Okay, but I can only retrieve the version 255.
Both of my devices are using this version right now.

Debug ID: D722221758

Then we'd want to see a Debug ID for a direct connection.

No, It is supported.
You can see that the PC logs I provided show that PROPFIND returns a 401 status code, but the synchronization is working fine.
Other software also works just fine.
I am re-deploying the environment on localhost; please wait a moment.

server: cloudflare

That's still Cloudflare.

No, it's returning server: cloudflare and other Cloudflare headers. It's literally a Cloudflare server responding to the HTTP request.

If you're going to post here, you're going to have to trust that we know what we're talking about. You provided a debug log that shows Cloudflare servers responding to the app's HTTP request. Perhaps a DNS record is still cached somewhere in the Android network stack — you'll need to figure that out. But we cannot help you until you provide debug output for a direct connection to your WebDAV server.

Re: your edit: it would be a TTL (time-to-live) on the DNS record — there's no "broadcast" — but yes, essentially.

New Debug ID: D944720143
There should be the directed address no problems now.

You're right, it's the TTL. This is the new Debug log package.
This time, there should be no Cloudflare relay involved. >-<

Yes, I have seen the backend request logs.
However, accessing the subpaths under webdav requires authentication.
Otherwise, it returns a null value.
You can try to directly access the root directory of that site using A segment of routine UA .
I have now unzipped the WAF.

Okay, I think I understand now. I have turned off the gzip package, but it still doesn’t seem to work correctly?

Hello, I conducted more tests regarding this issue.
The test results show that if I use the following command:

curl -X OPTIONS -u 'username:password' -H 'User-Agent: MyClient/1.0' 'https://your-webdav-server.com/path/' -v

It includes the username and password, returns the following response:

< allow: OPTIONS, DELETE, MOVE, COPY, PROPFIND, LOCK, UNLOCK, PROPPATCH>`
However, if the `-u 'username:password'

section is omitted, the response is:

< allow: OPTIONS, LOCK, PUT, MKCOL>

I believe this is the cause of the authentication failure on the Android side.
And this seems to have nothing different with whether the gzip package is enabled or not.

This has nothing to do with gzip.
I executed the following command and obtained the following output:

└─$ curl -v --compressed -X PROPFIND -u '<EMAIL>:<PASSWORD>' -H 'User-Agent: MyClient/1.0' 'https://<WEBDAV_DOMAIN>/dav/zotero/'

    * Host <WEBDAV_DOMAIN>:443 was resolved.
* IPv6: <IPv6>, <IPv6>
* IPv4: <IPv4>, <IPv4>
*   Trying <IPv4>:443...
*   Trying [<IPv6>]:443...
* Immediate connect fail for <IPv6>: Network is unreachable
*   Trying [<IPv6>]:443...
* Immediate connect fail for <IPv6>: Network is unreachable
* Connected to <WEBDAV_DOMAIN> (<IPv4>) port 443
* ALPN: curl offers h2,http/1.1
* TLSv1.3 (OUT), TLS handshake, Client hello (1):
*  CAfile: /etc/ssl/certs/ca-certificates.crt
*  CApath: /etc/ssl/certs
* TLSv1.3 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
* TLSv1.2 (IN), TLS handshake, Server finished (14):
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
* TLSv1.2 (OUT), TLS change cipher, Change cipher spec (1):
* TLSv1.2 (OUT), TLS handshake, Finished (20):
* TLSv1.2 (IN), TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-ECDSA-CHACHA20-POLY1305 / X25519 / id-ecPublicKey
* ALPN: server accepted h2
* Server certificate:
*  subject: CN=<ROOT_DOMAIN>
*  start date: May 20 23:00:43 2026 GMT
*  expire date: Aug 18 23:58:12 2026 GMT
*  subjectAltName: host "<WEBDAV_DOMAIN>" matched cert's "*<ROOT_DOMAIN>"
*  issuer: C=US; O=Google Trust Services; CN=WE1
*  SSL certificate verify ok.
*   Certificate level 0: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA256
*   Certificate level 1: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA384
*   Certificate level 2: Public key type EC/secp384r1 (384/192 Bits/secBits), signed using ecdsa-with-SHA384
* using HTTP/2
* Server auth using Basic with user '<EMAIL>'
* [HTTP/2] [1] OPENED stream for https://<WEBDAV_DOMAIN>/dav/zotero/
* [HTTP/2] [1] [:method: PROPFIND]
* [HTTP/2] [1] [:scheme: https]
* [HTTP/2] [1] [:authority: <WEBDAV_DOMAIN>]
* [HTTP/2] [1] [:path: /dav/zotero/]
* [HTTP/2] [1] [authorization: Basic <BASE64_CREDENTIALS>]
* [HTTP/2] [1] [accept: */*]
* [HTTP/2] [1] [accept-encoding: deflate, gzip, br, zstd]
* [HTTP/2] [1] [user-agent: MyClient/1.0]
> PROPFIND /dav/zotero/ HTTP/2
> Host: <WEBDAV_DOMAIN>
> Authorization: Basic <BASE64_CREDENTIALS>
> Accept: */*
> Accept-Encoding: deflate, gzip, br, zstd
> User-Agent: MyClient/1.0
>
< HTTP/2 207
< date: Fri, 03 Jul 2026 01:08:07 GMT
< content-type: text/xml; charset=utf-8
< nel: {"report_to":"cf-nel","success_fraction":0.0,"max_age":604800}
< cache-control: private, no-cache
< content-encoding: gzip
< vary: Accept-Encoding
< set-cookie: sl-session=<SESSION>; SameSite=None; Secure; Path=/; Max-Age=86400; HttpOnly
< strict-transport-security: max-age=15768000;
< cf-cache-status: DYNAMIC
< report-to: {"group":"cf-nel","max_age":604800,"endpoints":[{"url":"https://<CF_REPORT_DOMAIN>/report/v4?s=..."}]}
< server: cloudflare
< cf-ray: <CF_RAY>
<
<?xml version="1.0" encoding="UTF-8"?><D:multistatus xmlns:D="DAV:"><D:response><D:href>/dav/zotero/</D:href><D:propstat><D:prop><D:quota-used-bytes><QUOTA></D:quota-used-bytes><D:resourcetype><D:collection xmlns:D="DAV:"/></D:resourcetype><D:displayname><DIR_NAME></D:displayname><D:supportedlock><D:lockentry xmlns:D="DAV:">
...
...

The content has been desensitized.
The file content of the server can be obtained correctly.
Or is it that the Android version does not support gzip?

I don't understand what you're talking about.
At first, you said it was because the server was using Cloudflare, and then you said the server didn't support PROPFIND.
But I've already proven both of those points for you.
As for the return length being 0 even though gzip is claimed to be used, that doesn't make sense;
there's no data to compress in the first place, so it doesn't really matter. Or do you think the ideal content-length returned by OPTIONS shouldn't be 0?

The comparison of my OPTIONS tests above shows that the methods obtained after authentication are completely inconsistent.
Additionally, all the programs that use WEBDAV are working properly except for Zotero Android.

Here is the comparison of the results for the OPTIONS request.

curl -v --compressed -X OPTIONS -u '[USER@EMAIL.COM]:[PASSWORD]' -H 'User-Agent: MyClient/1.0' 'https://[WEBDAV_DOMAIN]/dav/[APP_DIR_1]/'

* Host [WEBDAV_DOMAIN]:443 was resolved.
* IPv6: [SERVER_IPv6_1], [SERVER_IPv6_2]
* IPv4: [SERVER_IPv4_1], [SERVER_IPv4_2]
* Trying [SERVER_IPv4_1]:443...
* Trying [[SERVER_IPv6_1]]:443...
* Immediate connect fail for [SERVER_IPv6_1]: Network is unreachable
* Trying [[SERVER_IPv6_2]]:443...
* Immediate connect fail for [SERVER_IPv6_2]: Network is unreachable
* Connected to [WEBDAV_DOMAIN] ([SERVER_IPv4_1]) port 443
* ALPN: curl offers h2,http/1.1
* TLSv1.3 (OUT), TLS handshake, Client hello (1):
* CAfile: /etc/ssl/certs/ca-certificates.crt
* CApath: /etc/ssl/certs
* TLSv1.3 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
* TLSv1.2 (IN), TLS handshake, Server finished (14):
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
* TLSv1.2 (OUT), TLS change cipher, Change cipher spec (1):
* TLSv1.2 (OUT), TLS handshake, Finished (20):
* TLSv1.2 (IN), TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-ECDSA-CHACHA20-POLY1305 / X25519 / id-ecPublicKey
* ALPN: server accepted h2
* Server certificate:
* subject: CN=[DOMAIN]
* start date: May 20 23:00:43 2026 GMT
* expire date: Aug 18 23:58:12 2026 GMT
* subjectAltName: host "[WEBDAV_DOMAIN]" matched cert's "*.[DOMAIN]"
* issuer: C=US; O=Google Trust Services; CN=WE1
* SSL certificate verify ok.
* Certificate level 0: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA256
* Certificate level 1: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA384
* Certificate level 2: Public key type EC/secp384r1 (384/192 Bits/secBits), signed using ecdsa-with-SHA384
* using HTTP/2
* Server auth using Basic with user '[USER@EMAIL.COM]'
* [HTTP/2] [1] OPENED stream for https://[WEBDAV_DOMAIN]/dav/[APP_DIR_1]/
* [HTTP/2] [1] [:method: OPTIONS]
* [HTTP/2] [1] [:scheme: https]
* [HTTP/2] [1] [:authority: [WEBDAV_DOMAIN]]
* [HTTP/2] [1] [:path: /dav/[APP_DIR_1]/]
* [HTTP/2] [1] [authorization: Basic [BASE64_AUTH_TOKEN]]
* [HTTP/2] [1] [accept: */*]
* [HTTP/2] [1] [accept-encoding: deflate, gzip, br, zstd]
* [HTTP/2] [1] [user-agent: MyClient/1.0]
> OPTIONS /dav/[APP_DIR_1]/ HTTP/2
> Host: [WEBDAV_DOMAIN]
> Authorization: Basic [BASE64_AUTH_TOKEN]
> Accept: */*
> Accept-Encoding: deflate, gzip, br, zstd
> User-Agent: MyClient/1.0
>
< HTTP/2 200
< date: Fri, 03 Jul 2026 09:54:22 GMT
< content-length: 0
< nel: {"report_to":"cf-nel","success_fraction":0.0,"max_age":604800}
< allow: OPTIONS, DELETE, MOVE, COPY, PROPFIND, LOCK, UNLOCK, PROPPATCH
< cache-control: private, no-cache
< content-encoding: gzip
< dav: 1, 2
< ms-author-via: DAV
< vary: Accept-Encoding
< set-cookie: sl-session=[SESSION_TOKEN_1]; SameSite=None; Secure; Path=/; Max-Age=86400; HttpOnly
< strict-transport-security: max-age=15768000;
< cf-cache-status: DYNAMIC
< report-to: {"group":"cf-nel","max_age":604800,"endpoints":[{"url":"https://a.nel.cloudflare.com/report/v4?s=[REPORT_TOKEN_1]"}]}
< server: cloudflare
< cf-ray: [CF_RAY_ID_1]
<
* Connection #0 to host [WEBDAV_DOMAIN] left intact

curl -v --compressed -X OPTIONS -H 'User-Agent: MyClient/1.0' 'https://[WEBDAV_DOMAIN]/dav/[APP_DIR_1]/'

* Host [WEBDAV_DOMAIN]:443 was resolved.
* IPv6: [SERVER_IPv6_2], [SERVER_IPv6_1]
* IPv4: [SERVER_IPv4_2], [SERVER_IPv4_1]
* Trying [SERVER_IPv4_2]:443...
* Trying [[SERVER_IPv6_2]]:443...
* Immediate connect fail for [SERVER_IPv6_2]: Network is unreachable
* Trying [[SERVER_IPv6_1]]:443...
* Immediate connect fail for [SERVER_IPv6_1]: Network is unreachable
* Connected to [WEBDAV_DOMAIN] ([SERVER_IPv4_2]) port 443
* ALPN: curl offers h2,http/1.1
* TLSv1.3 (OUT), TLS handshake, Client hello (1):
* CAfile: /etc/ssl/certs/ca-certificates.crt
* CApath: /etc/ssl/certs
* TLSv1.3 (IN), TLS handshake, Server hello (2):
* TLSv1.2 (IN), TLS handshake, Certificate (11):
* TLSv1.2 (IN), TLS handshake, Server key exchange (12):
* TLSv1.2 (IN), TLS handshake, Server finished (14):
* TLSv1.2 (OUT), TLS handshake, Client key exchange (16):
* TLSv1.2 (OUT), TLS change cipher, Change cipher spec (1):
* TLSv1.2 (OUT), TLS handshake, Finished (20):
* TLSv1.2 (IN), TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-ECDSA-CHACHA20-POLY1305 / X25519 / id-ecPublicKey
* ALPN: server accepted h2
* Server certificate:
* subject: CN=[DOMAIN]
* start date: May 20 23:00:43 2026 GMT
* expire date: Aug 18 23:58:12 2026 GMT
* subjectAltName: host "[WEBDAV_DOMAIN]" matched cert's "*.[DOMAIN]"
* issuer: C=US; O=Google Trust Services; CN=WE1
* SSL certificate verify ok.
* Certificate level 0: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA256
* Certificate level 1: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA384
* Certificate level 2: Public key type EC/secp384r1 (384/192 Bits/secBits), signed using ecdsa-with-SHA384
* using HTTP/2
* [HTTP/2] [1] OPENED stream for https://[WEBDAV_DOMAIN]/dav/[APP_DIR_1]/
* [HTTP/2] [1] [:method: OPTIONS]
* [HTTP/2] [1] [:scheme: https]
* [HTTP/2] [1] [:authority: [WEBDAV_DOMAIN]]
* [HTTP/2] [1] [:path: /dav/[APP_DIR_1]/]
* [HTTP/2] [1] [accept: */*]
* [HTTP/2] [1] [accept-encoding: deflate, gzip, br, zstd]
* [HTTP/2] [1] [user-agent: MyClient/1.0]
> OPTIONS /dav/[APP_DIR_1]/ HTTP/2
> Host: [WEBDAV_DOMAIN]
> Accept: */*
> Accept-Encoding: deflate, gzip, br, zstd
> User-Agent: MyClient/1.0
>
< HTTP/2 200
< date: Fri, 03 Jul 2026 09:54:37 GMT
< content-length: 0
< nel: {"report_to":"cf-nel","success_fraction":0.0,"max_age":604800}
< allow: OPTIONS, LOCK, PUT, MKCOL
< cache-control: private, no-cache
< content-encoding: gzip
< dav: 1, 2
< ms-author-via: DAV
< vary: Accept-Encoding
< set-cookie: sl-session=[SESSION_TOKEN_2]; SameSite=None; Secure; Path=/; Max-Age=86400; HttpOnly
< strict-transport-security: max-age=15768000;
< cf-cache-status: DYNAMIC
< report-to: {"group":"cf-nel","max_age":604800,"endpoints":[{"url":"https://a.nel.cloudflare.com/report/v4?s=[REPORT_TOKEN_2]"}]}
< server: cloudflare
< cf-ray: [CF_RAY_ID_2]
<
* Connection #0 to host [WEBDAV_DOMAIN] left intact

Additional explanation:

Although, according to the server configuration, the gzip package itself will not work for content of this size.

But in reality, I added a new layer of Nginx in front of the webdav server and removed the

Content-Encoding

field in the header.

This has really resolved the issue, and now the links are working properly.
Thank you all for your help!