Hi @_rb
While searching for a solution on the Check MK forum, I came across a helpful comment by @andreas-doehler : Unknown Exception on Host Notification Pulls
“As you use the RAW edition it is best to grep over the Nagios core logs.
I think you have to many events inside you system. This leads to a problem with to big log files of your core and then to the timeout if you make some searches over the events.”
Because of the comment: “many events inside you system” I started to navigate to the “Monitor > System” and “System > History” sections, where I compiled lists of failed notifications and successful notifications. Surprisingly, after following this process, the notifications began functioning properly again.
Subsequently, I observed that, prior to the restoration of notifications, the event “Spooled mail to local mail transmission agent” was not visible in the events section on the main dashboard.
In summary, the notifications have been successfully restored, and the appearance of the “Spooled mail to local mail transmission agent” event indicates their proper functioning. It seems there might be a peculiar bug related to the handling huge number of events in Check MK.
Thank you all for the help!