OS works in external drive but not in the computer

Hi,

Can anybody help?

My NVMe SSD drive works perfectly in an external drive enclosure running Catalina but as soon as I plug into the motherboard it doesn’t boot.

It powers up with the fans etc but I get just a black screen and no USB power and no option to get into the BIOS. As soon as I take the OS drive out it boots up as a PC fine and everything works.

In the other NVME slot I have Windows 10 which works fine when the other NVME isn't installed.

The drive did work previously until I took it out and cloned it (including the EFI) now when I put it back in it doesn't work.

Could it be something to do with the boot loader?

Thanks.

Specs
Gigabyte Z490 VISION D
2x SSD - WD Black SN750 500GB M.2 NVMe
i7 10700k