When playing a video file, you will see an error 'Error loading media: File could not be played' as shown below. This is most likely that the file is corrupted during upload or partially uploaded or the video file format cannot be played by the HTML5 video player.
We recommend converting the video file in your local computer using tools like HandBrake (https://handbrake.fr/) or AnyVideoConvertor (http://www.any-video-converter.com/products/for_video_free/).
If MP4 format is giving you issues, try WEBM format and see it helps.
We recommend reading the following KB note:
We support the following file extensions: