Several people have identified the bug with some challenges, especially Dagon, that the match won't start because it doesn't fully load (only black screen with sparkles at the bottom).

For those who really want to complete them, here is a trick I found that fixed the issue when I shut the Xbox off before closing the game.

Since this work around takes several hours of waiting time, I suggest doing it when you are ready to walk away from your Xbox (for example, go to sleep/work/school).

Steps to fix black screen during challenge loading After you select the challenge and notice the black screen:

• 1) Press Xbox button on controller and return HOME

• 2) Hold the Xbox button to bring up power options and SHUT DOWN system

• 3) Wait several hours (sleep on it

• 4) Boot up Xbox and load Gwent

• 5) You will notice a prompt that says "Your controller has been disconnected"

• 6) Press A to continue and the game will pick up where you left off (start of challenge