Usually this error message appears in BES server Application Log and has been followed by messages like.

[SERVICE_RELAY_SESSION:xxxxxxxx] Relay Ping Response not received
[SRP] DispatcherSRP Connection dropped, Error=0
[SRP] Ping Response not received
[SERVICE_RELAY_SESSION:S30268090:017339d0] Too many relay ping failures – dropping connection. Failures: 10

Such errors may prevent normal BES server functionality . There are various symptoms
You  may experience issues with activation, address book lookup, email delivery.

Usually errors are been as result of bad network connectivity:

  1. Network adapter drivers
  2. FW on BES server or corporate firewall : Set monitoring to tcp port 3101
  3. Ping your

Go to BlackBerry Server Configuration and on BlackBerry Router tab check connectivity:
                 BlackBerry Router

Restart your blackberry services.