Shutdown the NUC completely (including unplug from wall). Wait 1 minute. Reconnect and boot back up. Check if drive is working.
If, at this point, if the drive is still not working, I suggest that you try connecting it to another PC (or to this PC using a USB adapter if you have one) and see if it works then.
Is Your Hard Disk detected in Bios?
Well, that was an easy fix and it WORKED! Thank you so much.