I experienced this after my opponent resigned, then I continued the game against Lord Rattington.
I played a Druid, then the prompt to choose one of the boons did not appear, locking me into the "Which Boon?" prompt and making the game unplayable.
I just experienced this during a 2-player game (sadly, i failed to capture the game number or the server.
The kingdom had:
- way of the turtle
- ghost
- catapult
- druid
I had Ghosted a Catapult at the previous Night phase, but i didn't want to trash anything from my hand at the start of the turn, so i used Way of the Turtle on the Ghosted Catapult twice. In this game state, i was unable to select a boon when playing a Druid.
If i did "undo" enough to actually play the Ghosted Catapult (trashing two cards from my hand) then i was able to select a boon when playing a Druid.