OK Guys,
first of all thanks for your help!
I made a mistake by switching Buttons. I always pressed "GROUND FAULT/OVERVOLTAGE Test" before Startup. Without pressing it, i doesent appear, but if i once press it, the X.GEN.C.C comes back and dont vanish anymore... (just tested it after perfect startup)
Is this switch maybe my personal "don't touch it" switch?? :)