Her — Highness.mkv.mp4

: In Windows, if "Hide extensions for known file types" is turned on, a user might see "Her Highness.mkv" and add ".mp4" to it, resulting in the actual name being Her Highness.mkv.mp4 .

To fix it, try removing the .mp4 from the end so the file returns to its original .mkv state. Her Highness.mkv.mp4

: Known for being an open-standard "everything bucket." It can hold unlimited tracks of video, audio, and—crucially—subtitles in one file. : In Windows, if "Hide extensions for known

The . This is how the operating system will currently try to read the file. Technical Suggestion : In Windows

: Someone might have tried to change the file type by typing .mp4 at the end without realizing the original .mkv extension was still there.