When Challenging Friends from the main friend interface (lower left corner), if a Challenge is sent and the player moves away from the page, i.e. to Decks, then the challenge is no longer accessible and new challenges cannot be sent. There is no way to cancel the challenge at this point and the game must be restarted. Nothing seems to fix this particular issue and it presents itself on both Mac and Windows systems.
When Challenging Friends from the main friend interface (lower left corner), if a Challenge is sent and the player moves away from the page, i.e. to Decks, then the challenge is no longer accessible and new challenges cannot be sent. There is no way to cancel the challenge at this point and the game must be restarted. Nothing seems to fix this particular issue and it presents itself on both Mac and Windows systems.