If renaming the file doesn't work and it still won't play, the "wrapper" might be broken. You can "remux" or convert it to a standard format:
Because of the potential format confusion, it is best to use a "universal" media player that can handle almost any codec. 01. Mom And Daughter.mkv.mp4
Drag the file into a Google Chrome tab. Chrome has built-in support for many common video codecs and may play it directly. 3. Fix the Filename (Remove Double Extension) If renaming the file doesn't work and it
A free tool to convert MKV to MP4 (or vice-versa) properly without just changing the name. 01. Mom And Daughter.mkv.mp4
Use VLC Media Player . It is free, open-source, and can play both MKV and MP4 files regardless of whether the extension is named correctly.