Why isn't the YouTube channel notification bell working on Firefox?

I'm not talking about the the main notification bell. I'm talking about the bell that you find on individual channels that allows you to select whether or not you want to receive notifications when those channels upload content. When I click on the bell, the grey selection circle appears, but the menu doesn't pop up. This is only happening in my Firefox browser. I tried disabling all Firefox add-ons, but that did nothing.