There's three components to the key we have:

1. the metal key
2. the RFID tag for the ignition
3. the radio control module for remote lock/unlocking, alarm

I take it you've put your metal key into the new plastic case. Did you also transplant the old RFID tag? If not, the ignition will not sense the correct RFID tag within the vicinity and you get no start. As far as I know, you cannot get a new or separate RFID tag. It must be the one programmed to your VIN from the MB key factory in Texas, which only comes with the key. Your replacement case did NOT come with an RFID tag unless it's one you ordered specifically for your VIN through the Chrysler dealer.

Try finding the small RFID tag in your chewed up case tag and installing it, or hold your old case up to the new one when trying to start. It has to be very close to work.

Let us know the outcome and we'll go from there.