You may have jumped too many BIOS updates at once. I would recommend that you do two things (in this order), (1) reinstall the latest BIOS release using the Recovery Method (documented here: BIOS Recovery Update Instructions for Intel® NUC) and (2) Clear CMOS (documented here: Clearing CMOS on Intel® NUC).
Hope this helps,
This message was posted on behalf of Intel Corporation
Thank you very much to N. Scott Pearson for the information posted previously.
Please try the steps provided above in order to fix the problem, sometimes this problem happens as it was mentioned above when you jump from an older BIOS version all the way to the latest one, what we recommend is to install at least a few versions in the middle.
In regard to Linux support, I just wanted to let you know that Intel does not test and validate Intel® NUC on Linux; however we know that a lot of NUC owners are using it successfully on many different Linux distros.
So, at this point the best thing to do will be to access your Linux distro's website and forums for peer assistance with this issue at:
Any questions, please let me know.