I’ve been login in with the same user name and password for years. A few days ago the player no longer recognizes it.
Maybe you should try contacting WD’s Technical Support about this.
To Contact WD for Technical Support
The link below will allow you to call support.
Maybe you should unplug it. wait one minute, plug it back in and try again. To “turn it off and turn it on” works wonders with many devices!