Hi Ron,
Bluetooth supports various different profiles. The one that you need for answering calls is the phone profile. It could very well be that your phone is connecting to the car, but with an audio profile (for streaming music) rather than the one you want. Also, if you happen to have some other bluetooth device with you, and were using it for telephone calls, then it could be that it is still connected to the phone with the needed phone profile. I have observed that a connected profile will not automatically jump between devices and I have needed to turn off my headset adapter, or manually disconnect it on the phone, before my in car unit can get this profile and I can make calls.
You may want to take a look at your bluetooth settings, for the list of paired devices, when you are in the car. There you will see if you truly are connected as you expect and with which profile.
Regards,
Eric.