Unity Firefox, Windows 10.

Hey,
My old laptop died, so I got myself a new one, which has Windows 10 on it.
I use FireFox as my browser.

I used to play games on a certain website which needs a Unity plug-in.
I've tried Downloading Unity multiple times, but nothing seems to work. It says it's installed and it showed up in my 'downloads' but there's nothing to be found in my plug-ins on Firefox.

During another download, I got this:

(Yes, that is my dog. ) Aaanyway.

I've tried 'ignoring' it, but that doesn't seem to work either..

Well. I'm horrible at explaining things, but the point it,
Unity doesn't download normally and there's no plug in showing up in Firefox.

Maybe someone here knows what the problem is.
If not, then I'd be quite sad and annoyed.

Thank you.