Have you powered off the box from the button at the back for a few seconds ?
Also, check the bables at the back of the box are plugged in and have not worked loose, and check the HDMI cable at the TV end.
Can you also try changing the source on the TV remote and check the TV itself is ok ?
If you have the tv box connected via the powerline adapters and the middle light is orange/red on these, then that will usually indicate the communication speed between the adapters is low. This however should not stop the actual TV box from showing something on screen, so it could be the box itself.
First, make sure the plug adapters are direct into wall sockets where possible. You can turn them both off for 10 seconds then turn them back on and see if the lights turn green.