I have several videos in a document library. Modern view - all mp4 - Read permissions for all internal users - only used for intranet content. I used the document library instead of the asset library/list format to avoid all the extra folders. BUT, I also have a smaller asset library that I used to test when everything stopped working. Last week - everything played in the browser (Edge, Chrome, and FireFox). Monday - blank screen. No player controls - nothing. Not even an error message. They just stopped playing!!