Which product and version specifically are you using? You can find the information in the footer of the web console
Also, are these Windows services you are monitoring via WMI or processes you're trying to hit via SNMP? If WMI is being used, then you need to follow this guide:
This will help you to see if the issue is do to WMI communication issues.
You can also try setting the DCOM and WMI proprerties as outlined here: