1. Try a different wall outlet
2. Ensure that you are using the right cables (HDMI, USB)
3. Restart the external device, then the TV
4. Check that the external device is connected correctly
5. Check if the settings are configured correctly
6. Make sure that the device is compatible with your Smart TV
7. Check the picture settings on your TV
8. Check if your TV is up-to-date with the latest firmware