I am hitting this same error and have tried all the suggestions on this post. https://www.paessler.com/knowledgebase/en/topic/59410-my-snmp-ibm-system-x-system-health-sensors-don-t-work-what-can-i-do
It worked for a while and then stopped and started returning this error. There seems to be no obvious configuration issue.
Other SNMP sensors works just fine. Only the System X sensors fail.
Are there any other troubleshooting steps?