Okay, it’s appeared on the TV now!!!It may seem dispiriting, but it all helps narrow down the cause.
We know the monitor itself is fine as it works with your Mac. Probably not the HDMI cables either, as it is highly unlikely that all three HDMI cables are faulty (and besides, at least one works when connecting your Mac to the monitor).
So we know the issue is with either the PC or its graphics card. Hopefully the tests with the TVs may give us a bit more info.