Did you set CK11 to pairing mode as below?
1. If no, please press and hold the volume knob for several seconds until the indicator flashes blue and red; try to search "Avantree CK11" on your bluetooth list and connect it.
2. If yes but still can't connect, please follow the below steps:
A. Unpair/forget unneeded bluetooth items in your phone Bluetooth list and turn off the bluetooth.
B. Reset your carkit and reboot.
C. Turn on Phone Bluetooth again and refresh/search for devices. Found "Avantree CK11" and connect.
If still failed, please kindly contact email@example.com for further assistant. Thank you.