While the Cook-Key® is connected to the Thermomix® TM5, and the device is turned on (green light). Do not disconnect the device from the Thermomix® ТМ5 as pulling it off!
Consider going into Menu -> Settings -> Eject Cook-Key®. After that, the device is going to shut down (stop shine in green), and you may disconnect the devices.
If the Thermomix® is turned off you may disconnect the Cook-key® directly, without turning the Thermomix® only to eject the Cook-Key®.
Important: Do not plug-out the Cook-key® from the Thermomix® while the devices are operating, doing that, you may permanently damage the Cook-Key®.