Upgrade Storagesome of my collections are missing after syncing
I am missing some of the collections in my zotero library after syncing with the online library after a member -who did not have my collections - had synced with the online library. Is there a backup somewhere of an older version of my library that I can retrieve?
1. unless that person had actively removed those collections, that is not the reason they disappeared for you. Sync only deletes/removes things that are actively deleted.
2. it is very likely that you still have all the items that were in those collections in "My Library" (or in the group library).
As for your question, you can try https://www.zotero.org/support/zotero_data#restoring_from_the_last_automatic_backup, though that's a bit trickier if this is a group library (because restore to server doesn't work).