Tampermonkey - Tumblr Posts

RIP old blue and our free will

...and they didn’t even bother to check the grammar.

I throw myself at the feet of fellow Tumblrites and beg for help. I use TamperMonkey on two sites, here and AO3. It has stopped working on both and all I get is the spinny graphic shown below. I've made sure everything is updated, reloaded Firefox, rebooted the computer, no love. Does anyone have a suggestion?