video is uploaded in rich-text-editor without any problem but when the content rendered in page, the below error has been occured in console.
Uncaught (in promise) DOMException: Failed to load because no supported source was found.
the information is not enough but the main reason that cause this issue is the file you are uploading, in my opinion convert the file and do it again. you can use this site for free https://video.online-convert.com/convert-to-mp4