First we need to get terminology straight.
You posted under Virtualmin but keep asking about Webmin.
Are their domains listed under the Virtualmin > List Virtual Severs tab?
Next. What do you mean by Installatron in Webmin?
If you mean the scripts provided to install things like Wordpress, you must do that from the individual domain. Choose the proper domain from the drop down and then, first choice on my install, Install scripts > available scripts.
Virtualmin installs Webmin. I don’t know where you are in the process, but if you are in a position to start over, start with the script. That way we know going forward you have a good clean install. Good luck. https://www.virtualmin.com/documentation/installation/automated/