If the carkit was connected with 2 phones, 10BS/10BP will automatically reconnect the Last-connected phone once power on. To ensure the success of auto re-connection with 2 phones, highly suggest you to activate Bluetooth on the 2 phones before you open the car door.
1. If the Last-connected phone can't automatically reconnect:
A. Please activate Bluetooth on the phone before you open the car door and then press once the volume knob to reconnect.
B. If it always can't reconnect with the phone please reset the carkit to factory default settings and re-pair it.
2. If it's not the Last-connected phone, you need to manually click "Avantree 10BS" on your phone to reconnect.
If above can't solve your problem, please kindly contact firstname.lastname@example.org and describe your issue.