It is possible that the subtitling is not enabled or that the subtitles are in a language that is different from the audio language. To troubleshoot the issue:

1. Verify that subtitles are enabled in your settings.
2. Check that the language settings for both subtitles and audio are correct.
3. Try restarting your device.
4. Check your connection is working properly.
5. Check the audio files being used to accompany the video.