Similar problem happened to me.
Last creature played was Westgate Regent, then play passed to opponent. Opponent drew a card, and then did nothing as his timer ran out. The timer was ready to take a spare timer. However, the timer stayed there, frozen at 0. Conceding the game did not work and just closed the menu, so the program had to be fully closed.
IzzetInitiate#70689
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Similar problem happened to me.
Last creature played was Westgate Regent, then play passed to opponent. Opponent drew a card, and then did nothing as his timer ran out. The timer was ready to take a spare timer. However, the timer stayed there, frozen at 0. Conceding the game did not work and just closed the menu, so the program had to be fully closed.