Couldn't choose blocker
I was attacked by an opponent's 2 vamps. Nothing was played that would have prevented blockers.. I chose my one creature to block with, it highlighted it in yellow (as it does when you're assigning blockers), but then wouldn't let me choose WHAT to block.
Furthermore, it wouldn't allow me to UNselect the blocker, nor to choose any other blockers.
My only option it would let me click was "No Blockers"