I found it best to leave the probe in the installed in the sump for a few days before attempting the calibration. Make sure all the wires are routed and the probe and calibration solutions are at the same temperature.
The first time a friend helped me calibrate we had to log into the old Fusion and enable the pm1 module, then do a bunch of other funky stuff. Took like half an hour, I mistakenly thought I was going to go through that ordeal again. Thankfully not!