I have finally got around to some testing.
the hdmi cable is fine and i can send a signal to the monitor from other sources, although it is not the same framerate as what is coming form Resolve or MC (23.976). In any case, I have output to this monitor before with the same framerate, although there was always a bit luck involved. To get it to output to the monitor from MC i would usually have to start up Resolve first, to do kind of a "kick-start"...but it would get the monitor working. I do get a signal from the SDI out to my FSI monitor...but no luck with HDMI out.
Maybe the card is bad...or the HDMI port is bad? Or...I am missing something simple, which is usually the case.
Davinci Resolve Studio 16.1.1 • 2018 MacBook Pro • 2.6 GHz Intel Core i7 • 32GB RAM • Radeon Pro Vega 20 4 GB • OSX 10.15.1