We are using service desk plus and for asset management it fails to scan the machines connected to our network. It ends up with the following errors,

1. Credentials is not configured

2. General failure while performing the operation 

3. Connection to the RPC server in the workstation failed

4. Failed to communicate the Agent.

We have configured the credentials, the port 9000 is enabled, at times it does scan at times it will fail. Need suggestion and help in regards to this ASAP.