There is no NVIDIA control panel on your computer to adjust video settings? If not, you'll need to reach out to NVIDIA.
It may sound like a silly question, but you are using the HDMI output and not using something like a display-port to HDMI, correct?
The Model 976, as a repeater device, will report to the connected equipment that it is capable of virtually everything - high color depths, frame rates, resolution, etc. If your source device is trying to send more than 18GBPS though, the bandwidth of HDMI 2.0, you can have this problem. For example, 4K/60 4:4:4 can only be done at 8 bit(s); if 10, or 12 bit color depth, you are over the capabilities of HDMI 2.0. You would need to set the chroma subsampling to 4:2:2 if wanting to do 4K/60 at 10 or 12 bit color depth.
Feel free to open a support ticket with answers to the aforementioned, at support.outlawaudio.com, once you have access to a control panel for your graphics' card and can both confirm and change your video settings.