1.) Ensure that actions have been associated for the attribute that generated the alarm. For example, if the CPU utilisation of the server exceeded the permissible levels and generated the alarm, navigate to Monitor page->Configure Alarm and ensure that Actions are associated with this attribute.
2.) If this is an Email action, from Action Drop down->View Action->Execute the action manually and check if the mail action works.
If it fails and points to an error related SMTP, then the action could not have been triggered due to the SMTP issue. To test SMTP server, refer this KB.
Note: If this is Helpdesk ticket action, refer this KB.
3.) If SMTP works, navigate to Admin->Action\Alarm settings tab and check if “Enable Action when alarms are generated” field is checked.
4.) If the above field is checked and the monitor is present in any of the groups, verify whether actions are enabled in the group level. This can be verified from the Monitor group view as show in the screenshot below.