Product photo or video upload error

Product photo or video upload error

Form one day to another it is not longer possible to upload any photos or videos at DJ-Catalog -> Product -> Photo or Video.

The error message says:
Your browser doesn't support HTML5, Flash, Silverlight and even HTML4! Please upgrade your browser!

Following browser I tried: Crome, Brave, Firefox, Safari - all the same errors

No JS errors in Chrome console are given