DN not getting registered

HI All,
In our setup we are frequents facing an issue . Sometimes DNs are not getting registered in Agent Desktop Application & throwing error "Communication to T-Server Open " . Any one know the Reason & resolution for the issue , kindly suggest .

In SIP Logs i am getting below message.

device is out-of-service
10:12:17.632 Trc 36002 Request rejected: error code 58(Out of service)
@10:12:17.6320 [0] 8.1.100.64 send_to_client: message EventError

Without fragment of T-Server log covering the issue where the DN comes to be out-of-service no body will be able to help you. Try to be more specific. The mentioned message has nothing to do with Genesys server component, but your agent app (I guess written on PSDK).