The LEVO uses an intermittent stirring technique in order to minimize potential aeration of your infusion and to keep your machine working long into the future. This means that the stirrer will cycle ON for 2 minutes and then OFF for 2 minutes, until the infusion is complete.
The stirrer will only activate after WARMING UP mode is completed and INFUSING mode begins, and it will pause whenever the lid is open. So unless you're a ninja, you can't actually watch it stir (but you can hear it!).
If you are still experiencing trouble with your LEVO you can submit a warranty claim here.