I'm assuming that your Adobe Shockwave Player plugin is out of date, and Firefox is therefore blocking it to protect you. To fix this, download the latest version of Adobe Shockwave Player here, double-click the downloaded file from the website, then install Shockwave Player using the on-screen program setup that appears. Be sure to restart your computer if setup prompts you to. After Shockwave Player has installed, close Firefox if it is open and then re-open it. Is your problem solved?

If your problem occurs after the plug-in was updated, then click the Menu button>Add-ons, go the the Plugins tab in Add-ons Manager, find Adobe Shockwave Player, drop down the menu to the right of its name, and select Always Activate.

hello, you appear to have multiple versions of the flash plugin installed - for a solution please refer to cor-el's answer here: https://support.mozilla.org/en-US/questions/983849

or https://forums.adobe.com/thread/1489272

Oh, I've just realised something. You actually have a new and outdated version of Shockwave Flash installed on Firefox simultaneously. You need to remove the old version.

But philipp has already answered, so please follow his advice.

https://helpx.adobe.com/security/products/flash-player/apsb14-27.html

Flash Player Plugin 10.3.183.66 to 15.0.0.242 (click-to-play) has been blocked for your protection. https://addons.mozilla.org/firefox/blocked/p794

Current supported versions of Flash player are at https://www.adobe.com/products/flashplayer/distribution3.html