Subtitles inside a .mkv file won't work
 

When subtitles are inside a matroska file, more often than not, they won't work.
Same problem with multiple Audio too

The problem is only with BSPlayer as VLC and MPC they do work
It also were the case that BSPlayer couldn't open H265 encoded files, but thankfully K-Lite Codecs did solve this.

It's obvious that BSPlayer has fallen behind. It really used to be in the front lines but it's more and more becoming obsolete.

Please update it to handle the latest codecs, multiple audio, and multiple subtitles

Have you found a solution to your problem?
I'm having the same problem. I'm trying to play the show Vikings which has internal subs, 12 of them to be precise. On both VLC and MPC they show up. On BSplayer it shows 'Right click - Subtitles - Primary - "No Subtitles"'.
To clarify: Its trying playing the subtitle: "no subtitles". When i try to open it with the subtitle editor it shows as empty.

I've played around with the settings as well as downloading, enabling and disabling codecs without succes.