Motherboard swap – UEFI boot problem

Hoping someone can help me with this one!

I’ve just swapped out an old P67 board for an MSI B450 Tomahawk Max II which defaults to UEFI and which seems to mean that everything has to go through the Windows Boot Manager.

Although I’ve pointed the BIOS at the 2TB SSD with Windows 10 on it, the only option when Windows Boot Manager comes up is the ancient Windows 7 install on an even more ancient 1TB HDD.

I can get the PC into Windows 10 by setting the BIOS to CMS mode which will then boot off the SSD without showing any kind of boot menu, but without being able to use UEFI mode I can’t upgrade the PC to Windows 11 (or use ReBAR if I wanted to).

Can anyone suggest how I get the Windows Boot Manager to recognise the Windows 10 installation with the BIOS in UEFI mode?

Thanks!