this is a copy and paste from a similar question about vod subtitles so some wont apply to you
from emporium
Question was do you know that the channel has subtitles, and the answer was they should That is obviously not knowing.
Just because they may have them in the original broadcasts, dvd or blurays, does not mean that they are encoded into the stream, or even that the streaming platform has them enabled. This is not an stbemu issue.
I don't know of any IPTV services that actively advertise that thier VOD collection all has subtitles, or that their live streams pass along any subtitles encoded into original stream.
Just like movies you download (from various sources). Some have subtitles integrated into the mkv container, and other don't. Those that do, work nicely on my plex server and clients, and for those that don't I either search for external SRT files and put them in same directory with proper naming or once in a while I'll decide to use mkvmerge to merge them into my mkv container to keep a cleaner looking library.