Subdomain redirects to main domain (NGINX and Cloudflare)

Greetings!

I am self hosting WordPress under Ubuntu and have a total of two sites so far (working great) and about to setup a third but this one is going to use a subdomain. I am hosting WordPress (Apache) on a VM (E.G VM-1) and NGINX on another (E.G. VM-2). I have WordPress downloaded and everything configured up to the point where I visit the URL and finish the setup. Problem is whenever I go to the subdomain, I get redirected to the main domain.

Here’s the NGINX server block for the main site:

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

    server {

        # SSL configuration

        listen 443 ssl http2;
        listen [::]:443 ssl http2;
        server_name MAINSITE.com www.MAINSITE.com;
        ssl        on;
        ssl_certificate         /etc/ssl/certs/MAINSITE/cert.pem;
        ssl_certificate_key     /etc/ssl/private/MAINSITE/key.pem;

        location / {
            proxy_pass https://192.168.140.14/;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
        }

        # Authenticated Origin Pulls
        ssl_client_certificate /etc/ssl/certs/cloudflare.crt;
        ssl_verify_client on;

        # Use only TLSv1.3 and TLSv1.2.
        ssl_protocols TLSv1.3 TLSv1.2;

        # Use only TLSv1.3 and TLSv1.2 with below cipher suites:
        ssl_ciphers "TLS13-CHACHA20-POLY1305-SHA256:TLS13-AES-256-GCM-SHA384:TLS13-AES-128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES128-GCM-SHA256";

        # Use only TLSv1.3 and TLSv1.2 and only strong ciphers with above curves:
        ssl_ecdh_curve X25519:secp521r1:secp384r1:prime256v1;

        # Use Strong Key Exchange
        ssl_dhparam /etc/nginx/dhparam_4096.pem;

        # Defend against the BEAST attack
        ssl_prefer_server_ciphers on;

    }

and here’s for the subdomain:

    server {
        listen 80;
        server_name SUBDOMAIN.MAINSITE.COM www.SUBDOMAIN.MAINSITE.COM;
        return 301 https://$server_name$request_uri;
    }

    server {

        # SSL configuration

        listen 443 ssl http2;
        listen [::]:443 ssl http2;
        server_name SUBDOMAIN.MAINSITE.COM www.SUBDOMAIN.MAINSITE.COM;
        ssl        on;
        ssl_certificate         /etc/ssl/certs/SUBDOMAIN.MAINSITE.COM/cert.pem;
        ssl_certificate_key     /etc/ssl/private/SUBDOMAIN.MAINSITE.COM/key.pem;

        location / {
            proxy_pass https://192.168.140.14/;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
        }

        # Authenticated Origin Pulls
        ssl_client_certificate /etc/ssl/certs/cloudflare.crt;
        ssl_verify_client on;

        # Use only TLSv1.3 and TLSv1.2.
        ssl_protocols TLSv1.3 TLSv1.2;

        # Use only TLSv1.3 and TLSv1.2 with below cipher suites:
        ssl_ciphers "TLS13-CHACHA20-POLY1305-SHA256:TLS13-AES-256-GCM-SHA384:TLS13-AES-128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES128-GCM-SHA256";

        # Use only TLSv1.3 and TLSv1.2 and only strong ciphers with above curves:
        ssl_ecdh_curve X25519:secp521r1:secp384r1:prime256v1;

        # Use Strong Key Exchange
        ssl_dhparam /etc/nginx/dhparam_4096.pem;

        # Defend against the BEAST attack
        ssl_prefer_server_ciphers on;

    }

The CNAME is configured properly under Cloudflare.

Any ideas what I am doing wrong?