Here are a few things to try when your Smart TV is unable to show subtitles for foreign language channels:

1. Disable the optional subtitles in your TV menus.
2. Change the audio or language settings on your TV to match the audio of the channel.
3. reboot the TV by unplugging the power cord for up to 1 minute.
4. Check the Subtitle setting on the TV's channel and channel-list settings.
5. Check the menu settings of cable/satellite service provider.
6. Check online forums for similar issues with the model of TV.