I've not succeeded with Android am asking here because Voipo's official support responded:
"Unfortunately we are not able to provide support for 3rd party devices or applications with our service as their are too many variables out of our control."

So my situation: I've got a Sprint HTC Evo, no longer connected to cell service but works fine on wifi. I've tried both Linphone and CSIPSimple and have the same results. I can initiate a call and receive a call successfully, but I cannot get sound to send or receive either direction with either sent or received calls.

Does it matter that my standard Voipo Grandstream adapter is still plugged in at home to attached standard phones? I don't want to disconnect that either. On my secure.voipo.com shows both Linphone and CSIPSimple as registered devices as well as the Grandstream device.