have you tried using other ports to see if it's the one port that's bad?
Otherwise, try resetting the Xbox display.
The following was copied and pasted directly from a support page on Xbox website. Here's the link if you want to read about other stuff involving display issues.
https
/support.xbox.com/en-US/xbox-one/console/tv-or-monitor-screen-is-blank-while-connected
Your screen is blank after you turn on the console
Confirm that both your TV and Xbox One console are turned on.
Check that your TV is set to the correct input signal (HDMI).
Check that the HDMI cable connection to your console is secure.
Check that the HDMI cable connection to your TV is secure.
Check that the HDMI cable is connected to the "out to TV" port on the console.
Perform a cold boot on your Xbox One console by holding the power button on the front of the console for approximately 10 seconds, and then turn it on again.
Reset your display settings. Here's how:
If there's a disc in the Xbox One console, eject it.
On the console, press and hold the Xbox button for five seconds to turn off the console.
Press and hold the Xbox button and the Eject button until you hear a beep to turn on the console. You will hear one beep right away and a second beep 10 seconds later. The power light will flash on before the second beep. DO NOT LET GO until the second beep occurs.
Note This will boot your console in low resolution mode (640 × 480). To reset this setting, go to System > Settings in the guide, select Display & sounds, Video options, and then TV Resolution.