1) Check if the HDMI cable is connected properly.
2) Make sure that the switch on your Smart TV is set to the correct HDMI channel.
3) Make sure the streaming device is powered on.
4) Restart the streaming device and your Smart TV.
5) Try a different HDMI port on your Smart TV.
6) Check that your streaming device has the latest system software installed.
7) Contact your TV manufacturer for further assistance.