Nginx Multiple domains

Are they all HTTPS first/default based sites or some non-HTTPS ? Using HTTPS with Letsencrypt SSL certificates provided by Centmin Mod ?

Have you setup the main hostname as per Getting Started Guide step 1? When you install Centmin Mod it's setup a main hostname nginx vhost host for server which is where Nginx default install index page is shown. Accessing server via IP address will show that page and it's correct and should be left as is as the main hostname site is also used for statistics pages outlined here. When you create a new Nginx vhost site via centmin.sh menu option 2, 22 or nv commands, you have a separate Nginx vhost directory structure. The differences are outlined on official Config file page and at Getting Started Guide step 1 and bottom of that page here.

What does your /usr/local/nginx/conf/conf.d/virtual.conf and /usr/local/nginx/conf/conf.d/yourdomain.com.conf contents look like ? Make sure virtual.conf main hostname's server_name isn't same as any added nginx vhost site's domain name as per Getting Started Guide step 1, the main hostname needs to be unique.

You can check via recursive grep filter for each of the three domain names in vhost directory at /usr/local/nginx/conf/conf.d

Code (Text):

grep -rnw 'yourdomain.com' /usr/local/nginx/conf/conf.d

check HTTP headers via curl for both HTTP (and HTTPS if you have HTTPS/SSL) for each of the 3 domains

Code (Text):

curl -I http://yourdomain.com
curl -I http://www.yourdomain.com
curl -I https://yourdomain.com
curl -I https://www.yourdomain.com
curl -I http://hostname.yourdomain.com

for posting code or output from commands to keep the formatting, you might want to use CODE tags for code How to use forum BBCODE code tags