I have troubleshoot this for a long time and it appears that notifications in SCOM 2012 have stop working.   The notification have work for about a day.  After a few hours, we have realize that the notification with IM and SMTP were not working anymore.  Have reboot the server without  any good result.  Have delete, subscrition, susbriber and channel et reconfigure without any good result.   No error on the Operation Manager console and no error in Event viewer. 

Very similair to this post: https://social.technet.microsoft.com/forums/systemcenter/en-US/98c07ba6-f0b6-4239-82e7-d14011bf1bdc/scom-2012-notifications-dont-work

Have try to install the KB, put it doesn't install on are Microsoft Server Windows 2012 R2 Data.  Same server and same config on another environnement and it work well.   

The server is up-to

Hi,

Do you mean you installed the KB2599651?

I would like to suggest you test email notification settings in Operations Manager by following the links below:

https://support.microsoft.com/kb/934756?wa=wsignin1.0

http://blogs.technet.com/b/momteam/archive/2009/05/19/notifications-test-tool.aspx

Here is another similar thread, please also refer to it:

https://social.technet.microsoft.com/Forums/en-US/6d881470-f920-4fe2-b0ca-5a0ba7ddfcb2/notifications-not-working-in-scom-2012?forum=operationsmanagergeneral

Regards,

Yan Li