Having the same issue it seems like, on my laptop (that I bought the game on) it run fine last night (have not double checked this morning yet), but I went to play on my desktop and I get the failed login error as above, and when I try the Microsoft store bypass it doesn't show me as owning the game.
I've cleared the credentials and deleted the dungeons folder from app data as well.
Please help T-T
I have no clue what happened but I logged in in my laptop to verify, ran a "repair" and then logged into the tower to show my friend the issue and the thing worked >.>