May not have been the problem here but I’ve had cases where a TV etc is reset or updated and defaults to non-UHD input mode while the attached HDMI peripherals have (still) been set to UHD mode and their output is un-recognisable to the TV which announces no signal or just sits there.
The TVs have a setting in the inputs menu to switch an input to UHD capable but that’s not the default
I believe more recent TVs handle this better
The TVs have a setting in the inputs menu to switch an input to UHD capable but that’s not the default
I believe more recent TVs handle this better