I pulled out my cass to program a new key fob now it won't start and I think it's the anti-theft how do I reset that

Hi, my name is Devin. I am an auto repair expert with the Car Genius team here at RepairPal. I'm sorry to hear you're having trouble with your 328i. The anti-theft system likely needs to be synchronized with the new key. After removing and reprogramming the CAS (Car Access System), the immobilizer or key may not be fully programmed or synced to the vehicle. First, double-check the locksmith's programming work. They may need to ensure the key's transponder matches the CAS. Additionally, a BMW diagnostic tool or software like ISTA/D or similar is often required to reinitialize the anti-theft system. If the CAS box wasn't appropriately reinstalled or connections were disturbed, that could also trigger issues. If these steps don't resolve it, a specialized shop or dealership with the right BMW equipment can sort it out. If you need more advice, have any other questions about your vehicle, or would like to get connected to a RepairPal Certified shop near you, we have you covered. Give us a call at 877-913-1554, and we will happily help you out!