Guys,
Two customers reported the same issue, and I think it is better
to write a message here. If you can pair the Bluetooth module with
your smartphone but you cannot send or receive signal, you
probably forget to connect the audio in and out - PA0 and DACL.
These two pins are not in the 4-pin header. Instead they are on
the PCB side. I write becase I know you don't read Assembly Manual
:p
BTW, if you cannot trigger TX, you should increase the Bluetooth
volume to the max. No worries about over driving it.

Thanks,
Adam