After deleting local folder "storage", syncing only on demand despite "at sync time" choice
On Zotero, I have a "My Library" and I have two group libraries. These were taking up too much space on my local machine, so I decided I wanted to clear out my local storage of the group libraries and only download attachments on as "as needed" basis. Unfortunately, Zotero standalone client does not seem to offer a way to delete the attachments corresponding to a locally stored group library in an efficient manner. The storage folder contains all attachment files with no organization by library. (It's possible to find items in a particular library one-by-one by searching through the Zotero standalone client and then deleting the files by hand, but this is infeasible for a large library.)
Therefore, I decided to quit the standalone client and delete the entire local storage folder (in MacOS Finder, not within Zotero). (I backed-up the folder on an external hard disk.) I then started up the standalone client and went to "Preferences>Sync>File Syncing>Sync attachment files in group libraries using Zotero storage" (which was checked) and set "Download files" to "as needed". However, as desired, I left "Download files" set to "at sync time" for "Preferences>Sync>File Syncing>Sync attachment files in My Library using [Zotero]" (which was also checked). Then I clicked the sync button, and the arrow spin for about a second, and then stopped. None of the attachments were downloaded. If I double-click on an item's attachment in the database of My Library, the PDF is downloaded and displayed, but none of the other items are.
I went to this page
https://www.zotero.org/support/kb/changes_not_syncing
and made sure I wasn't hitting any of those issues. I confirmed that "Sync automatically" and "Sync full-text contents" were checked under "Preferences>Sync>Data Syncing". I confirmed that if I clicked "Choose Libraries", there was a checkmark next to all 3 libraries. I double checked that I was logged into the correct Zotero account (I only have one). I wasn't getting a sync error (no red exclamation mark) and the sync was only taking a second or so; the green arrow stop rotating and the blue stop button went away. This is the only computer I have a Zotero standalone client on.
For debugging, I removed the "storage" folder again, restarted Zotero with debugging turned on, performed a sync, double-clicked on an item's attachment in My Library, and then tried to sync again. The Debug ID is D1374914242. This should show that the client downloaded just the one attachment.
Note that setting sync to "at sync time" for both My Library and the group libraries did not change anything. The Zotero client just refuses to download attachments except as needed.
I am running Zotero 5.0.77 on MacOS 10.15.1 (19B88).
Therefore, I decided to quit the standalone client and delete the entire local storage folder (in MacOS Finder, not within Zotero). (I backed-up the folder on an external hard disk.) I then started up the standalone client and went to "Preferences>Sync>File Syncing>Sync attachment files in group libraries using Zotero storage" (which was checked) and set "Download files" to "as needed". However, as desired, I left "Download files" set to "at sync time" for "Preferences>Sync>File Syncing>Sync attachment files in My Library using [Zotero]" (which was also checked). Then I clicked the sync button, and the arrow spin for about a second, and then stopped. None of the attachments were downloaded. If I double-click on an item's attachment in the database of My Library, the PDF is downloaded and displayed, but none of the other items are.
I went to this page
https://www.zotero.org/support/kb/changes_not_syncing
and made sure I wasn't hitting any of those issues. I confirmed that "Sync automatically" and "Sync full-text contents" were checked under "Preferences>Sync>Data Syncing". I confirmed that if I clicked "Choose Libraries", there was a checkmark next to all 3 libraries. I double checked that I was logged into the correct Zotero account (I only have one). I wasn't getting a sync error (no red exclamation mark) and the sync was only taking a second or so; the green arrow stop rotating and the blue stop button went away. This is the only computer I have a Zotero standalone client on.
For debugging, I removed the "storage" folder again, restarted Zotero with debugging turned on, performed a sync, double-clicked on an item's attachment in My Library, and then tried to sync again. The Debug ID is D1374914242. This should show that the client downloaded just the one attachment.
Note that setting sync to "at sync time" for both My Library and the group libraries did not change anything. The Zotero client just refuses to download attachments except as needed.
I am running Zotero 5.0.77 on MacOS 10.15.1 (19B88).
In any case, since you deleted the files outside of Zotero, you need to use Reset File Sync History from the Sync → Reset pane of the preferences to force it to check all files. (The relevant support page is Files Not Syncing, not the one you linked to.)
I did this again with debugging enabled. The Debug ID is D1002164935. Thanks very much for bearing with me.
To satisfy my own curiosity: Do you think if I had deleted just the PDFs in the "storage" folder (which appears to be the least-violent action necessary to get Zotero to stop storing PDF attachments locally for just group libraries, assuming it's unreasonable to find library-specific attachments by hand) rather than deleting the entire "storage" folder, this would have been avoided? Or might this reset have been necessary any time you remove files en-mass through the OS file manager?
Thanks again.