Switching a system from using Apache to nginx is not supported. I’m not sure how you have both options, actually, as it’s not really possible to use both on the same system.
I have nginx active, and apache not running. I created a website with apache via virtualmin as it woukdnt allow me to select nginx, i would normally later uncheck apache and check nginx. I never had a problem before until now.
You should have used the --bundle LEMP mode when installing, you would have gotten nginx and not Apache.
If you aren’t using Apache, you should uninstall it. You’re using a completely untested/unsupported configuration. Virtualmin doesn’t expect both to be installed, so it’s confused.