Hello Clarkie42, I am sorry to hear you are having problems with your system but let me help you.
- he resolution needed in order to access the Intel® Visual BIOS Setup when pressing the F2 key is 1024x768. So please make sure the monitor supports this screen sizes.
- Please check the HDMI cable you are using is 1.4a, since this is the only one that support audio and video.
- A few days ago we received a notification saying that During BIOS POST, vBIOS/GOP will only output to onboard HDMI or Display Port output. The USB monitor requires its specific OS driver to function properly in an OS environment as primary or secondary monitor. So, you cannot access BIOS if the NUC is connected to a USB display.
Please let me know the SA # of your system in order to find out which is the BIOS version of your system. We may try a BIOS update.