Replaced hardware can't boot OMV

I replaced motherboard and CPU due to motherboard damage. Old system specs below.

Got new Asrock B660M-ITX and 12 gen i5. Rebuilt system - OMV on 256 NVME is seen but not as a bootable device. Tried all BIOS settings - no luck.

I can boot Gparted and Rescuezilla from USB.

How can I make it boot?

Thanks for your input. I can't see any way to do this, this BIOS is unlike most.

Thanks I'm trying to avoid what you suggest, but I have a regen backup available as last resort. I'll buy new NVME if I go that way and keep existing one safe. I've Googled this a lot can't work out how to get legacy mode. Is this something to do with CSM? Their suggestion us using an external graphics card to enable this seem odd.

This Reddit post is about an Asus board but it looks like the same problem:

Aus der Community ASUS auf Reddit

Entdecke diesen Beitrag und mehr aus der Community ASUS

www.reddit.com

From the Reddit threat it seems you have to leave the GPU in, which isn't of use as I have one PCIE slot in mini-itx board. I'll buy new NVME and use the regen.

I installed OMV 7 on new NVME no problems. I copied a regen backup from 11 Oct and ran it - it ended with error wrong version.

Reinstalled OMV, did omv-upgrade - same result.

Any ideas from here?

Hey thanks for the help but I decided to manually reinstall everything.