@TheNils For new domains, the NS record sometimes takes to propagate. That error message means that it's not propagated to the Cloudron server yet. You can try this:SSH into the Cloudron host -t NS mydomaine.net (This should not display NXDOMAIN) If the above works, it should work on Cloudron as well. If not, can try sudo systemctl restart unbound and then try adding the domain again?
We will improve the error message to be more descriptive (https://git.cloudron.io/cloudron/box/issues/548).