TH400 kickdown switch

Long standing issues with a non-op TH400 kickdown switch (the one on the gas pedal assembly).

Already replaced the assumed faulty original switch with a new one when I had my old TH400 in
Then I replaced the transmision with a new TH400

Thought that between those 2 things I'd have a functioning kickdown. I've tested the switch "manually" by engaging it with my hand while driving. Nothing, so the issue is not with mounting.

Likely not the switch itself (replaced) or the electric solenoid in the trans (low odds of 2 units being both bad in 2 transmissions).

It is a simple 2 wire system (right?) where the switch completes the circuit. The wire from the switch to the trans is fine. The other wire to the power source at the panel looks fine. The harness connector looks fine.

So what do I check next?