SQL Server Agent is a Microsoft Windows service that executes scheduled administrative tasks, which are called jobs. SQL Server Agent uses SQL Server to store job information. Jobs contain one or more job steps. Each step contains its own task, for example, backing up a database. SQL Server Agent can run a job on a schedule, in response to a specific event, or on demand.
The SQL Server Agent is made up of the following components:
SQL jobs consist of one or more steps to be executed. Each step consists of a SQL statement. SQL Agent Jobs can be scheduled to run at specified times or at specified intervals.
SQL Alerts consist of a set of actions to occur when a specific event occurs (such as when a particular error occurs, or the database reaches a defined size). Alerts can include sending an email to the administrator, paging the administrator, or running a job to fix the problem.
Operators are people who can address problems with SQL Server. Operators can be identified through their network account or their email identifier. These are usually the people who alerts are sent to.
So could you check the log or events for the Jobs or Alerts or Operators that your SQL Agent is configured with to find the detailed reason so the issue could be diagnosed and then corrected.