I did a mistake!
I downloaded a ssh-key plugin from https://github.com/litesolutions/scm-ssh-plugin
I imported it to my scm-manager. And it asked me to Restart the service. And now I get this error:
Error 503 Service Unavailable
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How can I undo this? I saw too late that it was a bug in this plugin in scm-manager 1.45.
But scm-manager 1.46 is not a released version, it is a snapshot.
It is installed as a service on a Windows Server 2012 R2 machine.