I'm running LR Classic, 10.4, Windows 10, and my sync has stopped working (mostly) to Lightroom/LR Web. I can create a synced collection and it will show up in LR/LR Web. When I place a photo in that collection I see the cloud icon in the upper right change to a rotating circle for a brief time and it returns to the green check. I wait some time before checking LR/LR Web to make sure the sync has time but the photo never shows up. The collection shows zero files. If I copy the file to another, already successfully synced collection it never shows up.
I have renamed/removed the *Sync.lrdata file. I have rebuilt the sync'd files via preferences, all to no success. This has been rather frustrating as I like to edit on various platforms but I can't get my LR Classic files to sync.