I installed the AddonFirst and did not update the MainGame first. Which happened to a lot of guys according to google.
Open console by ~ or by Shift-Klicking ´ß (qwertz Keyboards)
debugmode 1
runscript openalldoors
debugmode 0
and it works.
Warning:
DO NOT use this if opening a door is supposed to trigger an event, you might get stucked in the storyline. (Which is quite rare, almost all triggers i found are behind the door. You can see almost all triggers shining yellow after the initial debugmode 1 command.)
DO NOT use this to open doors you are not suppoed to enter until a certain Chapter, you might get a crash.