Gorillion said

On the website Roblox.com, you can launch user-made games through your web browser (firefox). In order to do this, you download a plugin for firefox, which I had before I changed OSes. I've been using firefox for a long time on Windows 7. I've recently made the change to get Windows 10. Everything seems to have transferred fine, except for this Roblox Launcher Plugin. As many times as I install, reinstall, uninstall, restart, downloading the plugin from their site does nothing. This has only happened on Windows 7. I've used other browsers, such as chrome, and they don't have this issue. The program is on my computer, but Firefox refuses to install the plugin, for some reason. This is sort of a stretch to be sending for the Firefox support forum, but the Roblox support forum wasn't helpful at all. If anyone could help, I would greatly appreciate it.

Crap. Meant to say "This has only happened on Windows 10", not Windows 7.

Never used this but if it is indeed a Plugin and not a extension for Firefox then the fact that you are using Win64 may explain why it is not working.

With Win64 Firefox only the 64-bit Flash Player and Silverlight Plugins are white listed to run. If you want to use other Plugins in Firefox on Windows (for example Java) you need 32-bit Firefox and 32-bit Plugins.

www.mozilla.org/firefox/all/