I think that it's related to bios version. I have two identical boards Z270-P, one with latest bios version and and with factory 0810 version. Latest version bios I only get 7 working, the 0810 version 8 working exact same setup.
0810 can't be downloaded either from asus support page, strange.
How can I downgrade my bios ? Does anyone have any idea? I already try some ways but none of them worked.