Open the statistics page while a call is active. Do you see that the number of received packets increases constantly? If the number keeps zero, the voice data doesn't get the way to PhonerLite. NAT and firewall may the problem here. You can try to configure a STUN server in PhonerLite (e.g. stun.ekiga.net). That would normally help if NAT is the problem. If you have a problem with firewall, you have to edit the rules in your firewall.
If you see received packets but doesn't hear anything, please check if you have selected the right sound devices. Just right click in the microphone and speaker button in PhonerLite and chose the right device.