Sometimes it happens, that there are no more notifications from the Enterprise Manager.
This occurs often after problems on the database (out of space in the os...).
The notifications are one of the most important features of the Enterprise-Manager, you are warned if the space is too low or if something takes too much cpu, if the backup has succeeded and a lot of other things.
The sending of the notifications is done by jobs that are defined in the sysman schema.
To repair this jobs, just delete and resubmit them.
This can be done by logging in as "sysman" user, and executing following procedures: