I can't offer much specific advise as I barely ever see a Simplicity in my world, but am I correct that the safety switches worked before the solenoid replacement? Parts Tree shows a real basic schematic and from that it hardly looks like a wire could have gotten switched during the install. Were there extra wires that weren't hooked up before? From your description, it seems seat switch like. Test w/ multimeter and know that in some cases, "fool proof " connectors are used that will short the circuit across if left unplugged. these sometimes fail as well.