middle mouse wheel not working

Just downloaded Firefox and my middle mouse wheel isn't scrolling.

Tried opening in Troubleshooting mode, still not working.

Zero extensions.

Scrolling still works in everything that isn't Firefox.

I am running X Mouse, but scroll hasn't been modified at all. It still lights up when I move the mouse wheel.

Can anyone give me suggestions on what else I can try? (Running on Windows PC, if that matters.)