ERROR Long polling is not supported by device server

Hello,
I don't know if this repository is still maintained, but I may ask a question anyway...
I followed the readme, and I am blocked at the moment when I enter my Access Key I got in the Device connector.
It returns me 'Server Error' on the web browser and I can see in the command line
```
DEBUG Request [GET http://localhost:8080/v2/notification/pull] - status: 404
ERROR Long polling is not supported by device server. Stopping.
```
The same error is reported by mvn jetty mvn tomcat and java commands

Is there any way to progress ?
Kind regards