Here are some things to try when your Smart TV is not responding to the remote when using certain apps:

1. Check if your remote is using the correct batteries.
2. Reboot your Smart TV by unplugging the power.
3. Update your Smart TV software.
4. Check your remote signal range and use point objects if needed.
5. Perform a factory reset to restore your Smart TV to its default settings.
6. Replace your remote, remote batteries, and cables if needed.