I can report the same issue on the Itch.io Windows Desktop app with my Twine game for audio and videos. I opened a ticket about it on GIthub on February 4 but it never got answered:
https://github.com/itchio/itch.io/issues/1413
I ended up adding a warning inside the game detecting if the user is playing from the Itch.io Windows Desktop app and telling them to use a regular browser. This is a less than ideal solution.
For info, this is what I use to detect the Itch app internal browser:
// Itch.io internal browser setup.isItchBrowser = function() { return navigator.userAgent.includes(" itch/"); }