1. Ensure that streaming service settings are set to show subtitles.

2. Adjust the subtitle language settings in streaming service and smart TV.

3. Check for any updates available for the streaming service app and/or smart TV.

4. Reset network settings, check if subtitles are available on other devices.

5. If the streaming service is compatible with other streaming media devices, try streaming from those devices instead.

6. If there are certain movies or shows where subtitles are not appearing, try watching them on a different device.