Core Issue
One common reason for this problem is the Telco is blocking the multicast traffic to or from that router. Issue the debug ip rip events command to determine if the multicast updates are being sent (224.0.0.9).
Resolution
To resolve this problem, try issuing the neighbor ip-address command under Routing Information Protocol (RIP). Also, look for any misconfigued Access Control List (ACL) filters or distribute-list commands that may deny routes from being advertised in the routing updates.
For more information, refer to the Filtering Routing Information section of Configuring IP Routing Protocol-Independent Features.
