It didn't set. It just didn't. I'm not sure exactly how it went so sideways but I ended up having to pour both trays in the compost (sorry, trash-pick-up-people) and the event at school had to go on sans jello treats.
The important part is that everyone survived.
I'm still disappointed in the pre-packed glitter jello but I went hunting for a more impressively glittery jello recipe and found one over at 1 Fine Cookie. I'm into it.
Better luck next time!