Over the past several days, one of our nodes has rebooted several times due to power issues, but I have not received a single Reboot Alert, even though it is configured. I have tested the alert (using the Test button) and the Last Boot variable reports correctly, as it does when I view the device through NPM. I couple of weeks ago I upgraded the IOS on one of our switch stacks and rebooted it. I got the IOS Change alert, but not the reboot alert. What are the possible issues?