Boiler Surge Protector Issue: Light goes off when power is turned on

Howdy folks:

Strange wiring situation here and feedback would be appreciated. 09/2025, I had a Weil Mclain Eco Tec 80 installed. It's been running perfectly. A few videos popped up that strongly recommended installation of a surge protector or else the main board on the Eco Tec could get fried. No problem, I bought a Rectorseal RSH-50 and went to install it. Here's where the fun starts: I installed the RSH50 on the emergency switch located right next to the boiler. The switch has two hot wires and one ground with the white neutral being capped off. There is a second emergency cutoff switch upstairs. I hooked up the RSH50 using Wago connectors and when power is turned on at the main breaker, the RSH50 displays a green light. When I turn on the emergency switch, the green light goes out. The boiler runs fine with the light out, however, that seems to indicate that the surge protector is no longer protecting the boiler. Here are some photos of the safety switch and the wiring. PS, voltmeter showing 120v at each pole of the switch. I'm stumped and feedback would be appreciated. Thanks!

PS: maybe move the surge protector to the dedicated breaker in the main panel?