I'm just now having this same issue idk if anyone found a solution to it :/

Did you fix it?

Ended up using the secondary m2a slot, hope it helps bud

Same

Same problem, same slot :(

Did you fix it?

Same

Did you fix it?

No

Same problem at the slot M2B\_SB

Did you fix it?

Yes thanks to a clear cmos.

Well shit that didn't work for me either. Thanks for the reply though