Your IP clients or your PSTN clients do not hear ringback?
First, if it is a VoIp route, you have to check if ringback is coming from the other side (must be).
Then you have to set in the trunk/line routing group the option to relay call progres tones. And also – Force progress indicator alert (in the IP routing group).
As I already have said – it depends on your case.
T. Georgiev, QCSP.