I've had this issue as well,
Though in my case it was becasue I had my bot set as such
Unranked;Daily Quest
Ranked;XXXX deck
This used to work until recently, because after bot finished dailys it would just move on to whatever was next, but now it is stuck playing casual with deck specified for ranked.Solution is just remove all queued items, or set mode to no queue.
Although this might not be the issue you've got it was worth the shot.