If the sound doesn't come out from CK11, please check below:
1. Please make sure that CK11 is well connected with your phone; or you can try to play music through CK11 to confirm whether it is connected.
If not, pls check below to connect:
Normally, if CK11 has connected with your phone, when an incoming call comes in, CK11 will ring to announce and you can answer the call by pressing the volume button on CK11.
2. If connected but it still doesn't work, it might because of your phone setting.
For some Android mobile phone, please make sure the profile for Phone Audio and Media Audio are both activated.
Method: Phone settings - Bluetooth - Paired Devices - Avantree CK11(a setting symbol behind it) - Active both Phone and Media profile.
Note: If you want to hear from CK11 in the call, please press the volume button to answer the phone calls, instead of answering from phone.
After doing above, the sound should come out from CK11. If not, pls drop an email at firstname.lastname@example.org. We will have further assistant.