Infuse Pro: subtitles not appearing

I’m currently watching a series (.mkv file) with the subtitles incorporated in the video file itself. When I play it on my laptop using vlc media player, the subtitles appear. But when I try to play it on Infuse (via iPhone), it doesn’t. The subtitle settings are set to show subtitles. And the options for subtitles show that there is an english subtitle file. But even if it’s selected, it still doesn’t appear. Anyone who can help?