I tried doing what others have said worked, without success.
Specifically:
1) Removed iCloud Sync from a Macbook that was still syncing correctly
2) Made backup on Macbook that couldn't sync.
3) Used the "Erase Everything" option on the Macbook that couldn't sync
4) Removed Enpass application from "Applications" (and removing from Trash)
5) Went to App Store and re-downloaded Enpass
6) Imported Backup file
7) Waited a bit, then tried to turn on iCloud Sync
Still sits on syncing for me on the Macbook that never worked.