For some Android mobile phone, such as Samsung / MOTO / LG etc. , please make sure the profile for Telephone Audio and Music Audio were active.
Please follow the below steps to active the above two profile:
Step 1. Choose "Settings" on your mobile.
Step 2. Find and choose "Bluetooth".
Step 3. Find the "Paired Devices".
Step 4. Find "Avantree BTCK-10B", there is a setting symbol behind it.
Step 5. Active both Telephone and Music profile.