Nagios Support Forum

Hi,
I'm trying to debug an odd issue.
Notifications for some services (but not all) have just stopped being generated. I can see the SERVICE ALERT event in the nagios.log file, but no associated SERVICE NOTIFICATION. I can see SERVICE NOTIFICATIONS for other alerts, and I can see these notifications/emails going out of the system via the maillog.
I am running XI3.2.
Is there anything else I can do to look into this? Nothing has been changed, and I have double checked that the services and contacts etc are set up as expected.
NagiosQL is working as expected, so there are no "stale" configuration files present.
Any ideas?

Is there any differences between the configs of the working and non working notifications?
Are only certain contacts working?

Basically, we are looking for any unique differences in the contacts/notification commands, the checks that generate the alerts, or the hosts those checks are run against.