Why won't iPad Settings let me turn on the Firefox Focus switch under Content Blockers?

I downloaded Firefox Focus onto my new iPad Pro. It works fine on its own, but if I want to use it with Safari, I cannot change the settings. I went to Settings > Safari > Content Blockers> Firefox Focus. I could not toggle the switch for Firefox Focus. The words "Firefox Focus" are not totally grayed-out, but they are definitely faded, as are the letters for my VPN.