EDIT: This fixed it once for me, but apparently is a longer-term fix for another user. I'm having other issues with the vehicle that might be related and made a separate post for them.
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Howdy all! First post. I called up the Uconnect customer service and got the fix to this problem.
Problem: Phone is connected via Bluetooth, playing music from phone to vehicle via Bluetooth. Turn vehicle off. Turn vehicle on, and audio reverts to FM radio.
Fix:
1. Sit in driver seat, doors closed, vehicle off.
2. Foot off the break, press start/stop button once to place vehicle in ACC mode.
3. Press the start/stop button twice to turn off vehicle.
4. Hold the Voice Recognition and Green Phone buttons on the steering wheel for 30 seconds, then let go.
5. Open the driver door for 30 seconds, or until the dash display cluster turns off - whichever comes first, then close the door.
6. Hold down the break pedal, and press the start/stop button to start the vehicle normally.
After I did step 6, my Uconnect system quickly flashed through several screens including what looked like a dial pad and the text "enter anti-theft code" (?). It still started in FM radio, but when I pressed the Media icon, it immediately went to Bluetooth (whereas in the past, I would have to hit the down arrow then select Bluetooth). I restarted the vehicle normally again, and this time it went straight to Bluetooth.
Let me know if you have any questions, or you can call Uconnect General Support here:
https://www.driveuconnect.com/contact-us.html
They asked for the last 8 characters of my VIN and had me verify my name, address, and phone number (which I assume they got through RAM). Edit: The second guy asked for my address and email, then asked if I wanted to add my phone number, so I guess they weren't for verification, but to add to their records.