So with the help and suggestions from Intel CC I got it working again.
The NUC refused to perform a BIOS downgrade using BIOS recovery method. I removed the SSD (850 Evo) and tried 0028 and 0033. Those didn't work (trust me I tried several times and left the NUC for at least 30 minutes). The NUC did absolutely nothing.
Then I tried 0024 without the SSD installed. The screen went on and the BIOS recovery worked. But my NUC still would not boot to BIOS. So I tried the BIOS recovery option again, but this time I used 0033. I figured 0024 worked, why not 0033. Flashed 0033 using BIOS recovery, placed the SSD back and voilá went straight to BIOS.
My NUC is up and running again!
If the NUC won't boot, nor give any output... Remove SSD and try 0024. For some reason only 0024 worked for me. The other two would not let my system boot. Screen would not lit, nothing!!
Thank you for joining the Intel communities.
I’m sorry for the issue you have experienced with this unit, I hope from now on your experience with the Intel® NUC can be much better.
I have seen some customer reporting that when they upgrade to BIOS version 0033 the M.2 is not recognized anymore.
A customer did the following:
“In case anyone reads this then be aware that once you update to BIOS 0033 you may need to enter Visual BIOS and change the option for M.2. SSD to 'on'. For some reason this setting defaults to 'off' on installing BIOS 0033 and may therefore result in your SSD not being recognized.
The setting is under Advanced --> Devices --> PCI tab --> M.2 slot
Check/Enable it then save and exit.”
A customer reported it at the following thread: