Nevermind, I just tried again to load it to the teensey and worked fine. Maybe it was some library that wasn't updated.
Thank you anyways.

Hello, I have a problem programing the teensey board that controls the buttons of the gameboy. I have downloaded arduino Ide and teensey software, but when I try to load the software provided in part 2 of the game boy zero guide (https://www.sudomod.com/game-boy-zero-guide-part-2/) an error pops up ...