The same is happening for me (trying to save from Amazon), except I'm using a
Mac OS 11.5.2 and Chrome 93.0.4577.82.

An example of a page that won't save is https://www.amazon.com/Black-Feminist-Thought-Consciousness-Empowerment/dp/0415964725. It's been ten minutes and it still says "Saving to" and the folder. I have tried all the suggestions on the troubleshooting page you shared. Other pages have saved fine, like those on my university's library website.

I have reloaded this and other pages many times. I have also restarted Chrome, restarted my computer, updated the Zotero extension, deleted the Zotero extension and reinstalled it, and so on. And still the Amazon pages just get stuck. So I will find other ways of saving citations for now. Maybe next week it will work again.

@nell_lake @dstillman

I've found what's causing this issue for me on Firefox:

Settings > Privacy & Security > HTTPS-Only Mode > Enable HTTPS-Only Mode in all windows.

After setting it to "Don’t enable HTTPS-Only Mode" it began working again. Looking at the HTTP requests Zotero Connector is doing:

http://127.0.0.1:23119
http://lx2.loc.gov:210
http://www.worldcat.org
http://www.lulu.com
http://loc.gov

I've tried adding all these addresses as exceptions plus amazon.com in "Enable HTTPS-Only Mode in all windows" to no avail.

Maybe it has something to do with these warnings about cookies

Cookie “AMCVS_0D15148954E6C5100A4C98BC%40AdobeOrg” will be soon treated as cross-site cookie against “http://lx2.loc.gov:210/LCDB?operation=searchRetrieve&version=1.1&query=bath.ISBN=^9781646084951&maximumRecords=1” because the scheme does not match. LCDB
Cookie “AMCV_0D15148954E6C5100A4C98BC%40AdobeOrg” will be soon treated as cross-site cookie against “http://lx2.loc.gov:210/LCDB?operation=searchRetrieve&version=1.1&query=bath.ISBN=^9781646084951&maximumRecords=1” because the scheme does not match.

zotero should try using https whenever available.

seems related https://github.com/zotero/zotero-connectors/pull/304

Yes, that LoC service doesn't support HTTPS. We've mentioned it to them, but they haven't fixed it. If you force that to HTTPS, many ISBNs won't resolve.

Chrome Zotero Extension will not save Amazon book Metadata to my local hard disc drive Zotero databank
Chrome Version: 98.0.4758.81 [Official Build, 64-bit] | Zotero version: 5.0.96.3 | Windows Version: Windows 10 Pro; version 20H2; 3/16/2021; OS build 19042.1466; Window Feature Experience Pack 120.2212.3920.0 | I have deactivated all my Chrome browser extensions except the Zotero one, after deleting my version and reinstalling the latest Chrome Zotero browser extension and I still cannot save Amazon metadata or Amazon data to my local [hard disc drive] Zotero databank! Why?

Thank you Dstillman for your prompt answer: Much appreciated: Yes for now the best thing to do is fetch book info via ISBN Zotero identifyer! Great Alternative: Thank you and standing by until everything is back to normal: Thank you so much!