So here’s how it was resolved:
Ulysses:
Your Mac seems to be affected by a bug that creates new groups when there are sync conflicts. In these groups, an important file of Ulysses is missing which is why the groups aren’t downloaded. Can you still find the files on other devices (insofar you own other ones)? If so, could you please move them to another group and see if they are synced?
Me:
The syncing issue appears to be across all of my devices. MacBook Pro, iPhone 8+, iPad Pro, iPad Air.
Ulysses:
Since the issue is appearing across all devices, it would be best if you do the following:
- Create new groups in Ulysses’ library
- Go to the menu “File” › “Browse Backups…” and select a date when the groups were still synced
- Drag the content from the backups to the new groups in the main window
So that’s what I did. Everything seems to be in order. I think I will start a redundant weekly plaintext backup in Dropbox or Devonthink to be extra double sure, though.