Bosch Smart Home Binding - Getting the device IDs

Hello, I installed the Bosch Smart Home Binding in OpenHAB 3.3.0.
Smart home center (Central) is installed and online.
The device IDs are required to configure the things.
To get this, a scan should be run.

Unfortunately, that doesn’t work for me. In the inbox → “+” → Binding, only “Ad manually” is displayed. No blue button to scan.

This means that no ID can be found in the events.log file either, since the devices cannot be found.

What to do to start automatic detection? Background Discovery doesn’t work either.