First, check the HDMI cable connection to make sure that it is properly connected to both the source device and the TV.

1. Check the display settings on the TV and make sure it is set to the proper display resolution.
2. Check the picture format settings on the TV to make sure that it is set to the correct format.
3. Verify the source device, such as a set-top box, Blu-Ray player, game console or streaming device, is set properly.
4. Check the connection type used to connect the source device to the TV to make sure that it is using an HDMI cable.
5. If available, check the audio and video settings of the source device to make sure that they are set correctly.

If the issue persists, contact the manufacturer of the source device or TV to troubleshoot further.