Xbox one has no display on TV only sound.... but then works ok on a pc monitor

I'm sure you've tried this but could it be the HDMI cable itself?

If you are still having issues this is sometime to try to reset your resolution

1. If there's a disc in the Xbox One console, eject it.
2. On the console, press and hold the Xbox button  for 10 seconds to turn off the console.
3. Press and hold the Xbox button  and the Eject button until you hear a beep to turn on the console. You’ll hear one beep right away and a second beep 10 seconds later. The power light
   will flash on before the second beep. Don’t let go until the second beep occurs.
   Note If you have an Xbox One S All-Digital Edition, you’ll need to press and hold the Xbox button  and the Bind button instead, as your console does not have an Eject button.
   
4. In either case, this will boot your console in low resolution mode (640 × 480). To reset this setting, press the Xbox button  to open the guide. Go to System > Settings > Display
   & sound > Video output, and then select the resolution you want from the Display dropdown.
5. If you’re required to complete these steps on every boot-up, you’ll want to change your TV connection to HDMI as shown in step 3 of the next section, "Your screen is blank and you use an AVR in your setup."

Do you only use your xbox on that tv or do you have something else that connects to it? Just incase it's actually the tv that's the issue

Thinking about it further have you tried any other ports on your tv? Also did you change your xbox resolution settings?

Podrias verificar que el cable HDMI no esste dañado

Do you use your tv for anything else other than your console? Is there are way to check if your screen works for normal tv or any other feature that doesn't need your console