If you have been sent a link to download this specific file, follow these best practices:

If the video is hosted on a website, you can use browser extensions like Video Downloader Professional to save it securely.

Are you trying to this specific video from a device, or did you receive a link to download it from someone else? Video Formats: Types of Video File Formats - Mailchimp

Sometimes files are incorrectly saved as PDFs; changing the extension back to .mp4 can occasionally restore playability .