secureboot with parrotOS – not able to sign custom kernel

I’ve installed Parrot OS on my surface and built the custom kernel for the surface from jakeday repo. I’m currently trying to sign my custom kernel that I can turn on secureboot again. I’ve followed the guide(https://github.com/jakeday/linux-surface/blob/master/SIGNING.md) and all works fine until step 5. After rebooting (with enabled & disabled secureboot) the “blue screen of…