Hi welcome to our forum. I take it the box won’t boot when you press the power button ?
First thing to try is turn off whatever the TV calls CEC control.
https://myhumax.org/forum/topic/hdmi-cec-known-as-by-manufacturer-1
You could also try selecting a different HDMI in on the TV, then press the 4000T power button wait a few seconds and re-select the right hdmi input.
The problem is likely down to a hdmi handshake issue.