Intel barebones nuc (RMA replacement) not detecting bootable m.2 ssd with win 10 on it

[Pacific Blue IT]

Bare box Intel BOXNUC8i7BEH
Have received identical NUC replacement under warranty return, installed ssd and ram and it couldn't find the original m.2 ssd with win 10 and clients data on it as a boot option, its detected in UEFI under devices m.2 por - ssd is fine was kept in a safe whilst nuc was being replaced and it opens fine in windows on my m.2 usb adapter and also opens fine when booting from Gandalf win 10 pe on the nuc - any idea why I can't boot from it or to make it bootable without a fresh install of windows?

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[Pacific Blue IT]

I'm just going through the process of making the boot partition active will give an update

 

[RCD_Technology_Solutions]

BIOS Version update?

 

[Diggs]

It opens but is it set as the bootable drive in the BIOS? I haven't been in to the BIOS of my NUC in years so I'm not sure what the options are.

 

[fincoder]

Maybe the original install wasn't installed in UEFI mode. Try enabling CSM / legacy BIOS.