I have seen this a few times so I’m copying my comment from another thread.
I’m having a similar issue. Commenting because I hope this topic gets seen. I have submitted a ticket but was told they could not do anything and I would need to wait for a fix from the forums. Being unable to play an entire game mode is frustrating.
For me, I play on mobile and PC and the problem persists across platforms.
link to my topic: Bug: Cannot retire/continue Duels run