I tried it now for some hours and can only think of that this is a bug.
I created an account for jenkins called scm with scm as password (very secure, i know, but for testing its enough). This account has administrator rights.
I also copied the api token from the scm user into the repository jenkins settings. And of course the url (http://server:8080/jenkins) and the project name. As token i use scm and as username i use scm. But still the same behavior. I have the feeling that jenkins is never getting called from scm manager. I am lost at the moment.
In general - jenkins configuration, i only entered the url http://server:8080/jenkins
Is there any way i can turn on debug logging or such? It would be really awesome if this would work.