Desktop sync client discovered previous sync journal(s) (SQLite database files: .sync_journal. db, .sync#HASH.db or `.sync_#HASH.db) in the folder.
That means the folder is either already used by a different client for syncing or there’s an old SQLite database file in that folder. This can also happen if a user tries to import an old folder.
Resolve
Such a file will have an old change date and usually can be removed.