There are a few things you can try in order to get external subtitles to display on your Smart TV:

1. Check subtitle file format:

   Ensure the external subtitle files are in a compatible format like .srt.

2. Check whether subtitles are turned on:

   Check the subtitles settings on the Smart TV.

3. Check video file format:

   Ensure the video file format is compatible with the Smart TV.

4. Configure external subtitle settings:

   Configure external subtitle setting on the Smart TV.