This KB might help: SolarWinds Knowledge Base :: Troubleshooting LEM Rules and Email Responses
You should see additional events in the "SolarWinds Events" filter (or start with the word Internal) that tell you why something failed. You'll also see errors in log data on the appliance, but that's a couple steps removed and a little harder to get to.
The "Initiated Action" event comes first, and it does tell you WHO the email is being sent to. As long as there are users there, and those users have email addresses, you should get to the next step of failure (or success) events which have much more info in them.
If the test email worked but the correlation rules are not firing (and hence not sending email notifications), it is most likely a time sync issue. Check this discussion