I guess the rear seats are on a separate circuit.
So I measured resistance on two connectors that go to the rear back rest. On one the resistance is 24.84 and on the other one 044.1
I'm no electrician but 044.1 seems like too little resistance? Those wires should be negative and positive, so the resistance should be infinite, since negative and positive shouldn't be touching each other, at least as far as I can tell! Not sure if 24.84 is acceptable though.

All fixed now. The problem was that I didn't connect the seat bench, just connected the back rests and I guess it needed the bench plug to be connected to close the circuit.