JupyterLab-Configurator not working

[tuxtof]

https://www.lean-data-science.com/ => This site can’t be reached

host www.lean-data-science.com 9.9.9.9
Using domain server:
Name: 9.9.9.9
Address: 9.9.9.9#53
Aliases:

Host www.lean-data-science.com not found: 3(NXDOMAIN)