If a device was connected or tried to connect, a one-time device token was requested and stored on the device. After a factory reset the token can get lost. In this case you need to reset the token in the Device Management Service.
- Open the Device Management Service
- Click on the three-point menu of the device whose Device Token you want to reset
- Click on [Reset Device Token]
- Confirm the security question in the dialog and start the process to reset the Device token
With a click on [Reset Device Token] the device token is deleted and a new certification process is enabled.