JS player in a post

Hi ! We need to add a JS player (an external js file like on http://staging-ge-test.ahph.fr/_tests/test-js-player-believe.html) on our product pages (this site is a record label shop). I'm working on the staging site. To make the issue simpler, I just added the player code to an empty page (https://indesens-staging.staging.wpmudev.host/?page_id=49125). Obviously WP is blocking the script, which is perfectly running on a simple HTML test page like http://staging-ge-test.ahph.fr/_tests/test-js-player-believe.html

After a three hours research, I tried many things to allow the script tag, disable kses etc. Nothing worked.

Would you have any advice or idea about this issue?