I had the same issue today on my Linux PC and Samsung S9+ phone... for whatever reason both just started requesting for password on OneDrive data in order to sync. Same as others, I haven't re-encrypted the data using some different password. Tried to delete everything from OneDrive, remove application access for Enpass on OneDrive and then re-establish the sync, but that didn't help, so only switching to different cloud service (DropBox) solved it.
Hopefully this is just temporary issue, because I really enjoy and appreciate the way Enpass just works... for years.