Ubuntu Domain join not working

Hey guys, if i try to join my Ubuntu machine to an ucs domain in testing i get an SSH Connection failed error from the gui. grafik
If i try to connect via SSH, wich i surely have done if i remember correctly. I get the following. grafik
I could need a hand here, to help me join my Ubuntu System to the domain.

Thanks and regards

Please post the join log under /var/log/univention/domain-join-cli.log