I'm running grbl 1.1 which uses pin 12 for the z limit switch. I've tested pin 12 on the arduino and it's fine - getting 5v. However, the "LZ" pin on the ST25 bob is showing zero volts. LX and LY are both ok - they show 5v.

Update 2/19/25 Ron got back to me - sent me a link to the instructions, which I had not seen before because I could not find them on the Tindie website, nor did they come with the product. This board was designed for an earlier version of grbl - not grbl 1.1 - so, pins 11 and 12 are swaped (the spindle enable and z limit pins). If you are using grbl 1.1, then you have to use the SE pin on the ST25 board for the LZ (z limit switch) pin and use the ST25 LZ pin for the SE (spindle enable). The instructions can be found at https://kclinear.com/st25 (not http://kclinear.com/st25). The note at the bottom of page 3 of the instructions is a little confusing, because it talks about the z pulse pin (rather than the z limit pin) being swapped with the spindle enable pin.