It's probably because you didn't associate the alert with a target - this is the most likely cause of alerts not working.

Have a look through the instructions here:

http://www.nessoft.com/multiping/manual/troubleshooting_alerts.html

When you look at the main MultiPing screen, any targets that are being monitored by an alert (any alert) have an [A] indicator in the first column. If that's not there, you won't get any notifications - no matter what conditions or events you have on the alert itself, because the alert doesn't yet know which targets you want it to watch.

If that's not the problem, the next step would be to have our support team look over the specifics of your situation. The best way to do that is to go to Help -> Email Nessoft Support, include the screenshot and then send that email to support (following the prompts there) so we can look at your alert setup and see if we can track it down.

- Pete