Predective dialing not working

We use broad band connection 2 mbps line. We are using vicidial 2.04 with asterisk server and slackware linux . It is working well with vicidial manual dialing for 6 seaters but in predictive mode in the live report screen it shows calls ringing, but the calls are not placed to the agents who logged in. i can see the leads being reduced but the agents are still waiting for the call.
Please we need help in this.
Please we need help in this.