Bluetooth Connectivity

I have a marine car receiver (Kenwood KMR d765BT) set up inside of my pool cabana with an amplifier and hardwired outdoor speakers. We normally pair through bluetooth to this unit via our cell phones to play music. The drawback is that the cellphone connectivity range in this case is limited to 10 - 15 feet. I am trying to increase the range by using  an Avantree rc-500 bluetooth receiver connected (via optical cable) to an Avantree Orbit Bluetooth transmitter. The Orbit recognizes the Kenwood receiver and attempts to pair via bluetooth, but the connection is never completed. Is there a known bluetooth connection incompatibility between these 2 units?