I too have the same issue, but I am using s2c modules ie 1 coordinator and 1 router.

When a frame is sent from Coordinator to Router, the “Transmit Request” frame displays Delivery Status as address not found(0x24) and Discovery Status as route discovery (0x02). The frame is not received at router end.

    When a frame is sent from router to coordinator, the "receive packet" frame is received at coordinator, but there is no "Transmit Request" frame is received at router end.
    In the network working mode, The coordinator is in active state and the router is in Inactive state. PAN IDs are same for both and SC=7FFF for both the modules with API mode.So what might be the issue here?? Any suggestions would be appreciated.
     What do you mean by " API packetize the command "CB4" " ??