Your Ancheer throttle is not just a throttle....
Meanwhile, the throttle part is probably just a 3 pin magnetic sensor chip, plus a magnet in the throttle. The chip wires are ground, 4.5V and throttle signal. Something is wrong in the throttle that short circuits the 4.5V power and that keeps the PAS from working.....
My understanding is that some e-bike throttles are nothing more than a 3-wire potentiometer with an output varying between 0 and +5V. I've not yet looked at the Ancheer throttle, however. I can't see why they would have to make it more complicated.