Was unable to get the HDMI port on the back of my Kona 4 to ever output from UE4, however using an SDI Monitor and connecting it to the out SDI4 cable from my Kona allowed me to stream from unreal. I have ordered an SDI to HDMI to use on a standard monitor and perform capture.
I have also managed to perform simultanous (BlackMagic → Kona → UE4)->ActiveGameTimeViewPort->Kona4->SDI Monitor. So I have a stream being sent into unreal, augmenting my virtual assets and streaming back to the kona and to a monitor in a single. It would seem the “No Frames ar available” warning is a suggestion of lost frames and is still occurring every now and again during runtime.
Accepting answer as this is a reasonable way to stream HDMI footage from unreal, all be it through one of the SDI ports and converted and not through the onboard HDMI port.