Hello,
You have not mentioned whether the tasks ever worked for you in this setup. As you mentioned that task status is not started, it means that the DS licenses are not expired other wise it would display message at the bigining when you create and execute the task. You can check the DS license status from Symantec Installation Manager (SIM) under licenses section.
You can even right click and the stop and delete the task and again execute it and check whether it is successul.