I was just playing the first mission you get when you join MTGArena and was about 4 stages in when my character died and the game crashed. Which then proceeded to crash my computer. When I tried to reset my computer it would not boot. I have tried reseting the entire computer and it has said there's been a problem. I've tried restoring a previous backup and it restored it then went to restart the computer. And once again when the computer restarted, it wouldn't boot. I was bluescreened and the pc went into automatic repair. I have been stuck on this for over an hour.
It sounds like you may need some more troubleshooting advice. Please review our Technical Troubleshooting articles for what advice we have available.