So my brothers PC has a 6700k, Asus Z170A and a reference 980Ti. I reinstalled Windows 10 for him but the issue is still there.
I install the newest Nvidia driver (388.31) and reboot. But upon rebooting only Geforce Experience is there. When I right click on the desktop there is no additional Nvidia options and Afterburner doesn't recognize any card and neither do games.. The drivers before 388.xx work fine.. Geforce Experience also always suggests an update of the driver when I check it.
I disconnected the internet just to be sure Windows wouldn't automatically install drivers and I also tried DDU.
More aboutweird nvidia driver issue
Did you change anything (hardware, software, BIOS option etc.) recently ? Try revert back it.
I uninstalled my drivers with DDU again and flashed another BIOS. After that I got it to install the new drivers.