A couple ideas.
It sounds like you are initiating the pairing from the iPhone. I usually do it from the headunit. I don't have an iPhone but I assume you can (in the phone's BT settings) make the phone discoverable. Then go to the headunit BT settings and search for the iPhone. You'll probably need to enter the headunit's pin on the phone. That code is visible in the AVIC BT settings.
Next thing to try when having pairing problems is to do a cold boot of the AVIC by disconnecting the car battery for around 30 seconds. Worth a shot. This often fixes problems after an AVIC firmware upgrade.
What firmware is your 940bt running? Have you updated it recently? Check the BT version too. The newest BT firmware (v3.32) has issues with some phones. IDK if yours is among them. i had to use older (v3.24) BT firmware on my Samsung Note 10S when I upgraded my phone. See BT 3.24 download