If the Device Authorisation access restriction is enabled, the device must be authorised to enable signing in. You can do it remotely or by signing in on the device as an administrator.
In order to authorise a device:
- Sign in as an administrator on the device which you want to authorise
- Click settings in the left sidebar
- In the Add-on settings section, click the access restriction button
- Click Device Authorisation in the menu on the left:
- Click the authorise this device button:
- The device will be added to the list of authorised devices.