My mother recently lost the keys to my 2006 Malibu Maxx. Went to a local dealership and had them cut a new one. The car was unlocked at my moms house, so I got in and coded the key then cranked it up. I then drove to work and locked the car. When I tried to leave, the key would not unlock the door. The dealer said that it can't be the key causing the problem. What do I do.