My issues with Gyazo GIF (and Replay) started about a week ago when I replaced my old MSI Geforce GTX 1060 with an Asus DUAL-RTX2070-O8G-MINI. The file loads up, even showing in my captures as a moving preview. Alas, when I try to play the .gif it fails saying "No video with supported format and MIME type found". I am on 79.0 (64-bit), yet it can be processed on Edge flawlessly.
Cleared cache, cockies, history etc., checked all media* in about:config, checked my mp4 codec, html5 etc., you name it - still to no avail. I am on Windows 10 (64-bit), Version 2004, OS Build 19041.388, running the latest Nvidia Driver 451.67.

Web Developer shows in Console:

"Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://i.gyazo.com/581e9....mp4

(Reason: CORS header 'Access-Control-Allow-Origin' missing).
All candidate resources failed to load. Media load paused."

Support is contacted, 2 mails exchanged a week ago.