I happen to have a SuperPINDA on hand that I was getting ready to install myself on my bear so took a few minutes to wire it up and test it out. I hooked it up to a Mini5+ on io3 to be as close to your config as possible.
First thing I thought that the probe was supposed to read zero until it triggers so I changed the line to
M558 P5 C"^io3.in" H5 F120 T6000 ;Removed the !
G31 P500 X23 Y5 Z2.5
Need to double check the ! but it triggers none the less.
Like @Veti said it is worth checking your wiring to make sure it is in the right place.
It should look similar to this
Blue = Ground
Brown = 5V
Black = Signal