1. Check if the correct cables are connected
Connect the correct cables to the external hard drive and then to the Smart TV. The type of cables you need vary based on the type of external hard drive you're trying to connect.

2. Check if the file formats are compatible
Make sure that the videos on the external hard drive are in a format that your Smart TV can read and play. You can look up the manufacturer's list of compatible formats.

3. Check for software updates
Software updates can sometimes fix streaming problems, so be sure to check if your Smart TV has the latest version of its operating system.

4. Connect to Wi-Fi
If the connection cable is not the right type or the file formats are compatible, try connecting to the TV's Wi-Fi connection. Certain Smart TV's can stream files from an external hard drive.