Are you sure it's the PATS? I swapped my PCM with an SVT one I picked up, came with a key but my lock cylinder obviously doesn't accept that key, and the PCM won't accept my original key so I have to cover the original key's transponder with aluminum foil and hold the other key to the lock cylinder to start it. If I just use my key and turn it it doesn't crank, all it does is flash the pats light rapidly.
Basically, if the PATS key isn't right or it's not finding the signal it WILL NOT crank. I'd check the crank sensor, with a small 7mm (IIRC) wrench it's really easy to reach from the pass. wheel well with the splash guard off.