Our Chev Silverado 2500 diesel is not starting and we put new battteries in. We have some electrical but door locks won't lock

Hello, ensure all fuses are intact and not blown. Check to ensure the vehicle is securely in the "PARK" or "NEUTRAL" gear. Ensure you have proper cable connections and no corrosion. The immobilizer function of the key may be a concern as well. Testing hands on is required.