Subdomain issues with HTTP and HTTPS for wordpress multisite

Question

I am new to Ubuntu server. I tried to set a wordpress multisite for a domain on nginx. I installed free ssl using lets encript. When I try to access the main website over http, it works fine. But when I try to access the subdomain over http, it shows me default apache server page. I am not getting where I made the mistake. The test website is:

http://friendflue.com - automatically redirects to https://friendflue.com

www.friendflue.com - returns default apache page (why?)

demo.friendflue.com - returns default apache page (why?)

https://www.friendflue.com - returns https://friendflue.com

https://demo.friendflue.com returns https://demo.friendflue.com

Here you can find the configuration for friendflue -

##################################
# WORDPRESS NGINX CONFIGURATIONS
##################################

server {
        listen 80;
        root /var/www/mywebsite;
        server_name mywebsite.com;
        return 301 https://$server_name$request_uri;
}

server {
        listen 443 ssl http2;
        root /var/www/mywebsite;
    access_log /var/log/nginx/wp_client_access.log;
    error_log /var/log/nginx/wp_client_error.log;
        server_name mywebsite.com;
    ssl_certificate /etc/letsencrypt/live/mywebsite.com/fullchain.pem;
        ssl_certificate_key /etc/letsencrypt/live/mywebsite.com/privkey.pem;

# Attempt to rewrite wordpress in sub directory 
rewrite ^/wp/([_0-9a-zA-Z-]+)/(xmlrpc\.php|wp-[0-9a-z-]+\.php) /wp/$2;
rewrite ^/wp/([_0-9a-zA-Z-]+)/(wp-(admin|content|includes).*) /wp/$2;


location / {
    index                               index.php index.html;
    try_files                           $uri $uri/ /index.php?$args;
}


#############
# Specify a charset
############
        charset                         utf-8;

############
# GZIP
###########

        gzip                            off;

#############
# Add trailing slash to */wp-admin requests.
############

        rewrite /wp-admin$ $scheme://$host$uri/ permanent;


############
# this prevents hidden files (beginning with a period) from being served
############

location ~ /\. {
        access_log                      off;
        log_not_found                   off;
        deny                            all;
}

###########
# SEND EXPIRES HEADERS AND TURN OFF 404 LOGGING
###########

        location ~* ^.+.(xml|ogg|ogv|svg|svgz|eot|otf|woff|mp4|ttf|css|rss|atom|js|jpg|jpeg|gif|png|ico|zip|tgz|gz|rar|bz2|doc|xls|exe|ppt|tar|mid|midi|wav|bmp|rtf)$ {
        access_log                      off;
        log_not_found                   off;
        expires                         max;
}

############
# Pass uploaded files to wp-includes/ms-files.php.
############

#       rewrite                         /files/$ /index.php last;

if ($uri !~ wp-content/plugins) {
        rewrite /files/(.+)$ /wp-includes/ms-files.php?file=$1 last;
}

# Rewrite multisite in a subdirectory '.../wp-.*' and '.../*.php'.
# if (!-e $request_filename) {
#    rewrite ^/[_0-9a-zA-Z-]+(/wp-.*) $1 last;
#    rewrite ^/[_0-9a-zA-Z-]+.*(/wp-admin/.*\.php)$ $1 last;
#    rewrite ^/[_0-9a-zA-Z-]+(/.*\.php)$ $1 last;
#}

# Rewrite multisite '.../wp-.*' and '.../*.php'.
if (!-e $request_filename) {
    rewrite /wp-admin$ $scheme://$host$uri/ permanent;
    rewrite ^/[_0-9a-zA-Z-]+(/wp-.*) /wp$1 last;
    rewrite ^/[_0-9a-zA-Z-]+(/.*\.php)$ /wp$1 last;
}


############
# Pass all .php files onto a php-fpm or php-cgi server
############

location ~ \.php$ {

        # Try the files specified in order. In our case, try the requested URI and if
        # that fails, try (successfully) to pass a 404 error.
        # zero day exploit defense

        try_files                       $uri =404;

        # Include the fastcgi_params defaults provided by nginx

        include                         /etc/nginx/fastcgi_params;

        # The amount of time for upstream to wait for a fastcgi process to send data.
        # We keep this *extremely* high so that one can be lazy when remote debugging.

        fastcgi_read_timeout            3600s;
        
         # Buffer size for reading the header of the backend FastCGI process.
        # This defaults to the value of a single fastcgi_buffers, so does not
        # need to be specified in our case, but it's good to be explicit.

        fastcgi_buffer_size             128k;

        # The number and size of the buffers into which the reply from the FastCGI
        # process in the backend is read.
        #
        # 4 buffers at 128k means that any reply by FastCGI greater than 512k goes
        # to disk and replies under 512k are handled directly in memory.

        fastcgi_buffers                 4 128k;

        # SCRIPT_FILENAME is a required parameter for things to work properly,
        # but was missing in the default fastcgi_params on upgrade to nginx 1.4.
        # We define it here to be sure that it exists.

        fastcgi_param                   SCRIPT_FILENAME $document_root$fastcgi_script_name;


 # Use the upstream for php7.0-fpm that we defined in nginx.conf

        fastcgi_pass                    unix:/run/php/php-fpm.sock;
        #fastcgi_pass                    127.0.0.1:9000;

        # And get to serving the file!

        fastcgi_index                   index.php;
}


############
# ROBOTS
###########

         location = /robots.txt {
               allow all;
               log_not_found off;
               access_log off;
        }


############
# RESTRICTIONS
############

# Deny access to any files with a .php extension in the uploads directory
# Works in sub-directory installs and also in multisite network
# Keep logging the requests to parse later (or to pass to firewall utilities such as fail2ban)
location ~* /(?:uploads|files)/.*\.php$ {
 deny all;
}

}

Answer 1

You need other blocks to manage www and subdomains, something like this:

server {
        listen 80;
        server_name demo.friendflue.com;
        return 301 https://$server_name$request_uri;
}


server {
        listen 80;
        server_name www.mywebsite.com;
        return 301 https://$server_name$request_uri;
}