Try installing Flash for Firefox.

Edge and Chrome both come with their own version of Flash (the Pepper version), where Firefox needs the Plugin version. Mozilla doesn't include Flash with Firefox because Flash isn't open source software, it's proprietary software and Mozilla "doesn't go down that road".

You can download the latest Flash Plugin version from here: Select the Windows > Plugin-based browsers - the EXE version. https://www.adobe.com/products/flashplayer/distribution3.html

Flash player doesn't solve anything, I've tried before multiple times.... Does it work for you?

The website uses for me a flash player.

Do you see the Shockwave Flash plugin on the about:addons page?

• "3-bar" menu button or Tools -> Add-ons -> Plugins

Do you see a Lego block icon at the left end of the location/address bar?

• https://support.mozilla.org/kb/why-do-i-have-click-activate-plugins

If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block content (e.g. Adblock Plus, NoScript, Flash Block, Ghostery) then make sure such extensions do not block content. There is security software that can interfere with loading content, so check that as well.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

It seems to work with disabled protection, I appreciate your efforts.