This is normally due to invalid information specified within the Credential being used. Try opening the Credential by going to "Configuration -> Credential List" and clicking the "Reinitialize" button. Once this is done, reenter the username using of the following formats:
For domain account:
For Local account
Reenter the password, confirm it and select the "Usage restrictions" that relate to the type of account this is.
Once this is all reentered and saved, try listing the services again.
Let me know if this helps.
Chris Foley - SolarWinds - Support Specialist
Support:866.530.8040 || Fax:512.857.0125
network management simplified | solarwinds.com