If 3729.mp4 won't open or has no thumbnail, it may be corrupted. Common causes include: Why is my mp4 video file unsupported? - Facebook
Most modern devices can open MP4 files natively. To view 3729.mp4 : 3729mp4
: Use VLC Media Player —a free, open-source tool that can play almost any MP4 regardless of the internal codec used. 2. Common Causes of Issues If 3729
: Right-click the file and select Open with > Windows Media Player or Movies & TV . 3729mp4