Failed to create virtual server. Nginx virtual host already exists

SYSTEM INFORMATION
OS type and version: Debian 10
Webmin version: 1.981
Virtualmin version: 6.17-3
Related products version: Flarum 1.0 /PHP 7,3

Failed to create virtual server : An Nginx virtual host with the same name already exists

I have an Nginx server with mixed PHP-FPM and Go server direct access. And I am trying to set up a forum using Flarum 1.0 (PHP).

Initially I used an other test domain that worked. (.org) and I no I am switching to a real domain (.net)

Where should I start to investigate this problem)?