I run a Nitto trailgrappler that is happiest at 32 psi. When it dips below freezing at night my stupid TPMS light comes on and will not go away. I have tried severaltimes to no avail to reset the threshold to 27psi. The JK honks twice, but wont shut the damn light off. I was able to verify the ProCal still works by playing with running lights, and i was able to just shut the TPMS off. I would like to set my threshold to 27 but the dip switch combo on the reference guide does not work. Does anyone know why its not working? I have checked the tires, and I verified I am following the right key position sequence by the other settings...

 

I had no problems w/mine, but here's what I'd try:
Fill tires up past 32psi to make sure the tpms warning light shuts off.
Disconnect the battery for a few minutes(reconnect).
Set the procal lower than the 27psi you want.

 

I had a similar issue, I had the Low tire pressure to High. When I called Pro-Cal they suggested I set the Low Tire alert to 8 lbs below the High pressure. It worked for me..