Your bluetooth headset must be compatible with the A2DP profile or else it will not work with this app.
If you are unsure about your headset, then a Google search for the specifications of your headset can answer a lot or you can email me and I can figure it out for you. Usually, if you can listen to music through the headset, then, more than likely, your headset is compatible!
If your headset is compatible with the A2DP profile, then under Bluetooth devices, your phone should say: "Connected to phone and media audio" If it just says media, then you will not hear either the ringer for incoming calls nor will you hear the talking caller id.
To fix this, repeatedly try pairing and un-pairing the phone (long press on your phone the button that represents your headset from within the Bluetooth Devices menu).
Another thing to try is enabling the option to "Disable ringer" when using A2DP, from the Incoming Callers menu.
Finally, try toggling the "Aggressive" option under Incoming Calls / A2DP.
We have found that a pause length of 2-3 seconds and looping of the notifications allows caller id information over bluetooth to work best!