Sorry for sking the obvious, but have you dbl checked your HDMI cables? 
Often times cables that are fine for 1080p fail at 4k...

Hello,

as Eric Mentioned an HDMI cable is really important when it comes to transmitting 4K signals. You need at least an HDMI 1.3/1.4 cable to be able to transmit 4K 60P.

Also, did you try getting the 4K signal with other apps?

Best regards,

Cable works Fine - 4k works with other Programs

Hello,

Please try to alter the In to Out Latency value in the video input Preferences tab.

Try to higher your current value until the signal works. Let us know if this helped solve the issue.

Best regards,