We have power back to the sunroom!
The electrician couldn’t figure out why we had an open neutral in that room. Couldn’t find a junction box or damaged wire that would lead to it. Did find a whole lot of Exciting wiring choices though, and fixed those.
He wound up running off of the neutral for another circuit, bypassing the damaged wire.
Choice quotes include:
“Huh. That’s new.”
“All 3 lights are on. I have no idea what that means.”
But the lights work again.