The most common reason subtitles don't load automatically is a naming mismatch. Your subtitle file and video file must have the exact same name, excluding the extension. Snowpiercer.2013.720p.BluRay.x264.[YTS.AG].mp4
If renaming doesn't work, you can force the player to recognize the file: subtitle Snowpiercer.2013.720p.BluRay.x264.[YTS...
Snowpiercer.2013.720p.BluRay.x264.[YTS.AG].srt 2. Manual Loading in Media Players The most common reason subtitles don't load automatically