WSUS 3.0 error

WebException: The request failed with HTTP status 404: Not Found.
at System. Web. Services. Protocols. SoapHttpClientProtocol .
ReadResponse(SoapClientMessage, WebResponse response, Stream
responseStream, Boolean asyncCall) at System. Web. Services.
Protocols. SoapHttpClientProtocol . Invoke(String methodName, ObjectU
parameters)
at Microsoft. UpdateServices . ServerSyncWebServices. ServerSync.
ServerSyncProxy. GetAuthConfig
at Microsoft. UpdateServices . ServerSync. ServerSyricLib .
InternetGetServerAuthConfig(ServerSyncProxy proxy,
WebServiceCommunicabonHelper webServiceHelper)
at Microsoft. UpdateServices . ServerSync. ServerSyncLib .
Authenticate(AuthorizationManager authorizabonManager, Boolean
checkExpirabon, ServerSyncProxy proxy, Cookie cookie,
WebServiceCommunicationHelper webServiceHelper)
at Microsoft. UpdateServices . ServerSync. CatalogSyncAgentCore.
SyncConfigUpdatesFromUSS
at Microsoft. UpdateServices . ServerSync. CatalogSyncAgentCore .
ExecuteSyncProtocol(Boolean allowRedirect)

Any ideas how to fix this ?