Ensure that the AR router can ping the ACS successfully.
Ensure that the AR router is configured with the same URL as the ACS.
Run the undo cwmp enable command and then the cwmp enable command in the CWMP view of the AR router to trigger a session connection.
If no connection is established, the AR router and ACS may fail to exchange packets. Capture packets on the ACS to locate the packet exchange failure. After the packet exchange failure is rectified, perform step 3 again to trigger a session connection.