To troubleshoot your Smart TV not displaying in high-definition, follow these steps:

1. Check that the TV is connected to a High-Definition Multimedia Interface (HDMI) cable.
2. Ensure that you are using the correct HDMI port.
3. Verify that the HDMI cable and display settings are both set up correctly.
4. If not already done, connect the TV to the internet
5. Check for new software updates and install them.
6. Reconnect the HDMI cable.