The NUC should work with the jumper located in normal position, pins 1 and 2, the option to leave the jumper disconnected is not something that we recommend to do because it might caused instability on the performance of the board.
On the following link you will find a description of the different scenarios related to the jumper, page 54:
The reason why is having that problem it is hard to tell, by trying the BIOS recovery to the latest version the issue should get fixed permanently:
So, make sure the BIOS settings are at defaults by pressing F9 once you get in the BIOS, then save the changes with F10.
If after the BIOS recovery is done the problem still persists, then it will be better to get in contact with the place of purchase because there might be a problem with the NUC itself, they will be able to let you know if they can do that for you, or remember that the NUC has 3 years of warranty with Intel as well.
Any further questions, please let me know.
Don't give up quite yet...
The standard things that you should do in this situation are as follows:
- Clear CMOS (see here: Intel NUC Clearing CMOS)
- Update to the latest BIOS using the Recovery Method (see here: Intel NUC BIOS Recovery Update Instructions)
- Reset the BIOS configuration (using F9 key in Visual BIOS).
I didn't see any indication that you had tried Step One. Despite what you've done before, try to do all three steps in order...
At the same time, please respond and let us know what hardware you installed into the NUC. Be explicit. What memory did you install (number of DIMM(s), DIMM part number(s))? What drives (SSD, HDD, SSHD) did you install? Did you install anything else (other than keyboard and mouse)?
Hope this helps,