There is a known issue downloading the subtitles of Shahid video, we currently are not sure when it can be resolved. Sorry for that.
Mona
Sigh...
As i have pointed out many, many, many times, StreamFab never adapted from providers that used to have HLS videos to when they switched to DASH videos.
Just for fun, i went to Shahid 5 minutes ago. I have no account and i have an ad blocker. When i tried to play the 1 free episode allowed, it blocked me saying to disable my ad blocker.
I did not disable it because all i needed was the .MPD file. I downloaded the MPD file and searched for subtitles. Of course, subtitles are there:

If you know how, it's extremely easy to download those subtitles. When you do, they are downloaded as separate, unplayable MP4 Files.
You then need to extract them from the MP4 into their native format and either keep them that way or convert them.
I extracted them as TTML and converted them so SRT.

It took me way longer to write this post than to download the subtitles.
This is the same issue that has been ongoing for over a year with Discovery+. I explained several times
how to download the DASH subtitles using Free Open Source Software and yet you won't do anything about it. What gives?