first the subtitle is a SRT file in the same folder of the movie I try both MAC and WINDOWS Plex Media Server the subtitle work just fine on the Plex Player inside MAC or Windows but did not work on roku client or popcorn client although English subtitle did not work also in popcorn player but it worked in roku player
I try to change all the sitting in both plex media server and client but nothing work any one can help plex is the perfect player for me but this issue is very frustrating
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update
"in Roku player arabic subtitle show in disconnected letters "
It worked in roku without any special setup but it show disconnected letters i can show you picture if you like but in popcorn a-400 no subtitle what so ever :(
I think the plex team have no plan to support arabic subtitle soon
I got the Arabic subtitles to work with roku client
1- rename your srt file to match the movie name and also give a hint to plex that it is Arabic, ex. The dark night rises.mkv the srt should be named The dark night rises.ar.mkv.