I am now having this same issue. I have installed NethServer multiple times with the same company (Hetzner) without issue, but now the network is breaking after install and the last thing I see is:
Created symlink from /etc/systemd/system/multi-user.target.wants/nethserver-config-network.service to /usr/lib/systemd/system/nethserver-config-network.service.
Any help would be appreciated!