Hello quite an old post but found the problem.
Disable all agent on the server exept the Agentless Management Agent.
Enable SNMP on the ILO, configure read community, trap community and destination and set the setting to agentless Management in the same page.
Be sure to delete the server and ILO, then only discover the ILO, if all goes right the ILO will be discovered, when data collection runs for the ILO the server should be added without any extra credentials. Be sure the SIM does not try to discover the server itself as this will cause the timeouts seen earlier.
Once the polling job has run you will also see the status for the server. The Agentless Management software can be downloaded from the hpe.com website.