You could also have a mismatch between sensor models.
There are 2 TPM sensors in the MoPar parts catalog:
Part # 68001696AB - Fits Chrysler and Dodge 2005-2007 model years
Part # 68001698AB - Fits Dodge (their computer tells them) 2008-2009 model years
MoparSuperCenter checked them both physically for me...looks like they're physically identical, the difference is the frequency the TPMS works at. So you need to match the frequency of the sensor you get to the frequency of your car. As far as he knew, the only real way to know is to pull one of your wheels and look at the TPMS. Although, he was reading a procedure that said something like "park the vehicle for a minimum of 20 minutes, then drive for at least 10 minutes at a constant 15 mph. During this time the vehicle will learn the TPMS frequency."
Good luck finding a road, or the patience, to drive at a constant 15 mph for 10 minutes!
NOTE: You'll see references in other, older posts on forums to 68001696AA...SAME SENSOR as 68001696AB, they've just changed the part number. So ask for 68001696AB.