ZD510 Bluetooth connection doesn't open

I have a demo app which is working perfectly to Tap-and-Pair with the ZQ610.  But this same code will not work with the ZD510.

I get a ConnectionException: "Could not connect to device: read failed, socket might closed or timeout "   when BluetoothConnection.open() is called.  The NFC tap is giving me the correct MAC address, and I've even tried hardcoding it to be sure.

I have tested the Tap-And-Pair app, and have verified my code against the ConnectivityDemo source.  Everything looks as if it should work (and it does with the ZQ610).

One other note... The Android Printer Setup app works perfectly with a tap.

Do I need to do something more / different with the ZD510?