This message was posted on behalf of Intel Corporation
mxplxxx: Thank you very much for joining the Intel® NUC communities. We are sorry to hear the NUC is not working as expected.
In order to try to fix this problem we can do a BIOS update to the latest version 0050 using the F7 method:
Besides that to install the latest graphics driver 4678 will be a good thing to try as well:
Another step will be to install the HDMI firmware update:
Which Windows version are you using?
Are you sure the HDMI cable is 2.0?
Did you check if by any chance the monitor has a firmware or driver update?
Any further questions please let me know.