You require a valid PHYSnet account (NOT alumni) & cluster access to login.
Read the cluster documentation on how to obtain cluster access:
https://git.physnet.uni-hamburg.de/physnet-docs/compute
Need help? Write to support@physnet.uni-hamburg.de

THIS IS A TESTING INSTANCE FOR PREPARING A COMPREHENSIVE UPGRADE OF THE PRODUCTIVE JHUB!
IT WILL SHUT DOWN, REBOOT, CHANGE APPEARANCE, BEHAVIOR AND FEATURES UNANNNOUNCED ANT ANY TIME!!!

You can already test your workflow here to ensure a smooth transition after the upgrade.
Please, report anything that is missing from your perspective directly to martin.stieben@uni-hamburg.de