Icecap ATO black sensor broken

Everything was working fine for 5-6 months, but when I moved it to a new sump, it starts to fill as long as the water line is below the white sensor and completely ignores the black (line) sensor. Once it fills past the white sensor, it starts to beat and won't stop until manually stopped. I've tried all sorts of things like cleaning the sensors, checking connections, making sure the pump line doesn't have siphon, and even switching the white and black sensor line plugs. Nothing works.

I'm going on a 10 day business trip today, which is very frustrating bc this is supposed to be one of the most important pieces of equipment I have and now I'm going to have my friend manually fill the tank. Pls resolve.