If you are streaming or opening files from a cloud service, check your router or re-download the file to rule out corruption.
If you are dealing with a bulk set of videos (e.g., 56 separate MP4s): 56 mp4
If your default player (QuickTime, Windows Media Player) won't play an MP4, try VLC Media Player , which supports nearly all video formats. If you are streaming or opening files from
Use tools to check if files are truly "unidentified developers" if they are downloaded from the internet, as Apple devices sometimes block them by default. If MP4s import into editors (like After Effects)
If MP4s import into editors (like After Effects) as green or broken, try disabling hardware-accelerated decoding in the application preferences. Managing Large Numbers of MP4 Files
Use file management software to organize large volumes of video data to prevent "metadata" issues where the computer cannot identify the video/audio tracks. If you can tell me more about: