Have a nosy at this link. Pay attention to the bottom where it says “get in touch” as this takes you to another page to contact via call about subtitles.
Also to add.
Can I assume you’ve done a reset to the TV?
Delete and reinstall the app?
If you can’t, try clearing the app cache.
Now does not respect the Subtitles setting on LG TVs.
For each individual programme, each time you watch except when viewing episodes back to back, you need to Pause the movie, look for a speech bubble symbol bottom left, navigate to it, choose the Subtitles option, and then press Play.