93 Plymouth Voyager minivan wont start or even click, even after batt replaced.

Hello, a battery showing 12 V does not indicate that it is fully charged or able to accept a load. It just means that there's 12 volts present, but it could be almost zero amps. As a result, you'll have to have the battery professionally tested for state of charge. Once you know you have a fully charged battery -- if the vehicle still does not start -- then testing must continue, checking battery cables for secure connection on both sides of each cable, plus being free of corrosion, checking the starter motor for the ability to crank, and checking all fuses to make sure none are blown. Beyond that -- yes, the "anti theft chip" could be the cause of your concern. These aftermarket (non-Chrysler) devices could be malfunctioning or perhaps that chip is inserted incorrectly. It's too hard to know without hands on testing. I would strongly recommend removing and defeating any of these devices, as you could be chasing the concern with no resolution when a non-factory device is installed and malfunctioning. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops