Is this a known issue? Thanks.
There is the odd occasion whereas a TV might report supporting a video mode that it doesn’t in reality and that can cause this. It can also happen with a bad HDMI cable. There is also the possibility in certain setups that CEC can change inputs to another device on startup and although it actually is outputting compatible video the display being on another input makes it seem otherwise. There is probable a few other situations as well that I’m just not recalling off hand. Can you plug it into a different display to see if it works there?