Stuff like this is why I keep printing entrance tickets and the like. I don't want to end up in a situation where I have to trust software that is known to have new bugs every months to get into a place without any sort of backup.
I almost got completely screwed by my pixel updating right before a concert while I was already out of town. Luckily my wife was able to login to my computer and forward the tickets to someone else that I was with, but it was a close call because she was walking out the door to do something herself when I managed to get ahold of her.
In this case, if you don’t have a phone that can display Ticketmaster’s code, you’re just SOL, since they decided to break being able to just print out your code.