Task Manager Stopped

Without research It is hard to say what might have caused this.  Definitely something you should open with support if it keeps happening.

For completeness I'm adding below the steps to check on the status of the task manager and how to start or resume it if necessary:

In cache terminal:

%SYS>d ^TASKMGR 

1) Create a Task
2) Edit a Task
3) List Tasks
4) Delete a Task
5) Suspend a Task
6) Resume a Task
7) Run a Task
8) Task Reports
9) Task Manager Options
10) Exit
 
Option? 9
 
1) Task Manager Information
2) Start Task Manager
3) Suspend Task Manager
4) Resume Task Manager
5) Task Manager History
6) Define Mail Settings
7) Exit
 
Option? 1
Task Manager Version: 2.9
Task Manager is currently suspended
Task History purged after 7 days
 
1) Task Manager Information
2) Start Task Manager
3) Suspend Task Manager
4) Resume Task Manager
5) Task Manager History
6) Define Mail Settings
7) Exit
 
Option?  <---Here you can choose to resume or start the task manager depending on the status from the Task Manager information returned in the step above.