Subtitles not showing up on infuse 6 with Plex Server

Hi.

I bought an apple tv4k on which I installed infuse.
I took a month pro subscription to test the app possibilities, but I have a questions.
Before I used Plex on all my devices.

I have Plex server on my nas synology DS216 to watch series (and movies) with subtitles.
For exemple, the nameof a tv show is:
tvshow.S01E01.mkv
tvshow.S01E01.srt (or .fr.srt)
in the same directory

I can see the series with infuse but impossible to see the subtitles while watching.
The DNLA option is activated on my server.

I didn’t find a solution in the forum, so does anyone have a solution? (smb, nfs, media server synology, …?)

Thank you for your help