I have usually encountered a similar issue about every 1-2 weeks, and it last occurred last Friday night. I usually have to do a bunch of power cycling and flipping settings back-and-forth on all equipment, but this last time it wouldn't work. I ended up switching my HDMI out to my TV to a different HDMI port on the TV. So far it has been OK for a week, but I've only turned on the player about 3 times since then.
I send my video out to the TV, and use the HDMI audio out to my receiver. I have this setting on the player set to auto.
I think I found my problem. It also wasn't outputting HDR. I have two projectors and my receiver has a HDMI output to each. I disconnected the older non 4k spare projector and now HDR is sent and haven't had an issue with the player going dark again (at least yet).