I have two servers behind on IP address. Server1 is hosting several websites all using TLS exclusively.
Recently I set up Server2 and setup one website using reverse proxy from Server1 and finally successfully deployed TLS on it as well.
During that setup I had to use port 80 to use Certbot with Let's Encrypt.
Now I'm trying to do it again the same way with another domain.
The proxy_pass directive works on port 8080, but when I switch it to port 80 I get a 404 error.

Here is setup in question: (again, Port 8080 works, but port 80 does not)

----------------------------------
#Proxy server (Server1)

# threedaystubble.com server
server {
listen 80;
server_name www.threedaystubble.com threedaystubble.com;
location / {
proxy_pass http://192.168.3.5:80;
}
}


#Proxied Server (Server2)

server {
listen 80;

server_name threedaystubble.com www.threedaystubble.com;

root /var/www/threedaystubble.com;

location / {
}

}

--------------------------------------

Also, I checked if anything was happening on port 80 on both machines with net stat -plant:

Server1
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN -

Server2
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 0.0.0.0:8080 0.0.0.0:* LISTEN -
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN -

Any help would be greatly appreciated.