You have followed the instructions in KB - https://kaseya.zendesk.com/entries/88631707-Agent-Offline-alerts-are-not-generated-since-upgrade-to-R9
The process fails with the error: /inc/suspendUpdate.inc, line 152
This issue happens when there is an issue with the Monitor -> Suspend values.
WORKAROUND / SOLUTION:
Remove the suspensions on all machines, and just re-apply them.
You can then re-run the emailNotify.asp (see https://kaseya.zendesk.com/entries/88631707-Agent-Offline-alerts-are-not-generated-since-upgrade-to-R9 for instructions) and check that you get a blank page and that the error is gone.
If the error is still there, it is likely that you have suspensions applied to other machines that you have not yet re-applied.
TIPS / TRICKS:
To avoid having to go through every page and find the machines with suspends in place, you can run this SQL query to give you the list of machines that currently have an alert suspension in place.
If you are not confident running SQL queries, please contact support by logging in to https://helpdesk.kaseya.com and mention this article.
SELECT v.displayname FROM monitorsuspend m
JOIN vAgentLabel v
ON m.agentguid = v.agentguid