Do you have validation rules specified? Do you display validation errors on the form; you can add this to the form view template temporarily to display any errors coming from the validator:
@musbah I imagine if you’re trying to upload MP4 video files then they’re going to be large files, so you’ll be hitting some limits somewhere (whether it be file upload limits or timeout limits).
Instead, you should look into multi-part (chunked) uploading of large files such as videos.