Do you have a few pictures of how you tied in the 2n2222a transistor to the probe, or which pin on the transistor gets the brown wire and which gets red from the DC-PSU? Assuming you’ve soldered it to the brown wire? Looking at your hand sketch, you have the + going to the +36V. Looking at KSK they recommend a voltage between 10-30VDC. If I tied the brown to a 24v PSU (DC), would you see that working as well?