In the end of the installation was the write of MBR successful?
I think I had some issues where the install tried to write to the wrong device so in the end (where GRUB is being handled) I had to remove my usb drive from the NUC and attempt again, then it succeeded and the next screen was that the box wants to reboot. Could this be the case in your case?
That is that GRUB was never written to your MBR so the drive isnt bootable?
