The Thermomix® sold in the USA is not designed for use with a converter.
Using one can cause damage to the unit, and repairs are only authorized for 110V UL-certified models. You can see the "UL" logo on the bottom of the Thermomix®. It represents that it is compliant with the USA standards of safety. If you need a repair service for a non-UL Thermomix, please contact the distributor where you purchased it from.
Ensure your Thermomix® TM5®/TM6® is connected to a power supply with 110/127V AC and a frequency of 50 to 60 Hz, as marked on the plug.