I did have an issue with a storage array that was a known issue with HP. A firmware upgrade fixed the issue and iLO shows all system health as good.
The PRTG SNMP sensor for "HP ProLiant System Health" still shows a "Failed" state. I'm not sure what it is seeing that iLO is not. All channels within the sensor are good, other than the "Overall Status" channel.
Is there something that needs to be cleared somehow? I deleted the sensor and added it back and the same issue occurs. Certainly there could still be an issue with the server, but iLO doesn't seem to think so.