Firefox doesn't use ActiveX controls, so there's no ActiveX filtering to turn off.

Many sites use the Flash player plugin to play videos. Next to your post (Question Details > More System Details), your plugin list doesn't include the Shockwave Flash plugin. Did you intentionally disable or remove it? If not, Firefox might have disabled it because it was too out of date.

To update Flash, you can download the current installer from this page:

https://get.adobe.com/flashplayer/

Please uncheck any unwanted extras in the center column (if you do not see the center column, and you use an ad blocker, use its icon to make an exception for the page so you can control what gets downloaded).

Does that help?

When it comes to the Flash Player, there are different versions for each of the major web browsers. Google Chrome comes with its own version of Flash; IE uses the ActiveX version; whereas Firefox needs the Plugin version.

You can download the latest Flash Plugin version from here: Select the Firefox and Netscape Plug-In - compatible applications – NPAPI - get the EXE installer version. https://www.adobe.com/products/flashplayer/distribution3.html

When you get it from there, you won't be offered the unwanted "extras".