Please be aware ingredients that are taken directly from the fridge, or liquids that are not room temperature, can cool the bowl and therefore slow the heating of the Thermomix.
There is a simple tests that can be done to check the heating function of a Thermomix®.
Test 1: Place an empty mixing bowl in your Thermomix, set the Thermomix to 3 min / 250°F / Speed 1. If the temperature is not reached, it is likely the heating mechanism is malfunctioning; call Service at 888-867-9375 for next steps.