interactive video not recognizing mp4 format anymore

Hello,

in moodle 3.6, h5p latest release, interacive video content, it worked fine up to this morning when no mp4 files made available through a link to the moodle streaming repository woudl be recognized. The video opens with a "video format unsupported" message on a black rectangle. The problem affects every mp4 file video available on site. I tried to create new content with same file but to no avail. However donloading the file and playing it on my desktop work with every possible player I could think of. Trying to upload the file directly into IV doesn't work either, there will be a red notice saying the contentId parameter is missing.

Technical staff suggest it might be a remote problem as nothing has been recently changed at this end.

In the middle of a course, approaching exams makes students really nervous. 

Please, any suggestions or help out of this mud?

Many thanks

Adriano