I have a NUC7i5BNK and I use 2 BENQ monitors. One is connected to the computer using the HDMI port and the second is connected through the USB-C port. After more than a year of use, my second monitor started to go off intermittently, coming back after some cable changes, plug/unplug, etc. Yesterday it went off for good and never came back when used through the USB-C port. I changed monitors and cables, etc. The monitor itself is OK, cable is OK, so my fear is that the USB-C port is defective. How can I find out if the port is really sick?
Sorry @TDean, but that won't (necessarily) help him. He could be using the port for USB activity without issue and still have a problem with the passthrough of the DP signal.
All that said, I would be willing to bet that the issue is a failure in the dongle being used to extract (and possibly modify) the DP signal. I would try using another dongle.
Hope this helps,