After upgrading my BIOS from 1301 to 1902 using EZ Update/USB I cannot seem to return to 1301. I first tried installing 1301 using EZ Update with a USB flash drive in the BIOS as I did for 1902, but it claimed the file X299D.CAP was "not a proper BIOS". I then used the flashback button on the rear panel. After that it would not post and there was a message "Code 05" on the motherboard's lcd. I then re-did flashback with 1902 and it still wouldn't post. I then hit the Clear CMOS (CLR_CMOS) button and it posted to 1902 (and I was very, very glad).

I'd like to return to 1301 because in 1902 Hyper-V will not run. I've selected virtualization in the BIOS, Windows says virtualization in enabled in the task manager, but if I try to start VMs I get the message "hyperviosr isn't running". Everything worked in 1301. I may create a separate post on this.

Suggestions very welcome on what to try next.

I 'm wondering if I should try flackback with 1301 plus the cmos button if necessary as this seemed to help with 1902.

Thanks!

Motherboard: PRIME X299-DELUXE
OS: Windows 10 Pro 1809 Build 17763.615