Check the voltages at the step-up connector with your multimeter: verify that your power taps are good.
Where are you getting ground? Check your ground continuity to the ground braid to make sure it's good. I just tap the ground braid directly.
You can then verify the circuit is working by unplugging from the Q24 harness connector and briefly touch that P1 signal wire to ground braid. Knocker should go off.