Make sure you can read those files. Open the file manager and try to open them. If you can’t, change their permissions to give yourself read permission. If you can, then please share with me their permission setup (and the permission setup of all parent folders).
Had to wait for a backup to complete to be sure, but that did it. Weirdly, recently-used.xbel was already set to the correct permissions, but wouldn’t back up until I set the other files and ran it again.