1) Check to make sure your TV's firmware is up-to-date.
2) Reset the app.
3) Force stop the app then restart it from your home screen.
4) Uninstall the app, then reinstall it from the app store.
5) Clear data and cache of the app.
6) Update the app by visiting the manufacturer's website and follow the download instructions.
7) Make sure that the app is optimised for the specific Smart TV model.