NUC not booting after HA OS update

Hi All, Please help if you can.

I have just updated to the latest version (9.5?) and after the install the NUC wont boot.

I see GNU GRUB with 4 options - Slot A, Slot B, Slot A rescue shell, Slot B rescue shell.
Selecting any of them results in a blank screen, no errors, nothing.

Is there anything i could try to get it booting again? Thank you!