Reactjs – why can't I open my http webapp in the browser with nginx?

Only localhost can access server_ip:port_no, but other devices can’t. It always show not secure with blank page and static files I place in nginx are not showing either. When I inspecting the browser, it shows

:8443/favicon.ico:1 
Failed to load resource: net::ERR_SSL_PROTOCOL_ERROR

I checked TCP connection with netstat -an | findstr :8443 just to ensure and it shows list of my server_ip and other devices listening correctly. I also manually enable inbound firewall rules with port 8443. Didn’t work. I just want other devices to access my webapp on the same internal network.

This is my nginx.conf with only http protocol.

http {
    include       mime.types;
    default_type  application/octet-stream;

    sendfile        on;
    keepalive_timeout  65;

    server {
        listen 8443;
        server_name 192.168.xxx.xx;

        root html;
        index index.html index.htm;

        location / {
            try_files $uri $uri/ /index.html;
        }

        location /api/ {
            proxy_pass http://localhost:8050;
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection 'upgrade';
            proxy_set_header Host $host;
            proxy_cache_bypass $http_upgrade;
        }

        location /static/ {
            try_files $uri =404;
        }

        location ~* .(js)$ {
            try_files $uri =404;
        }

        location ~* .(css)$ {
            try_files $uri =404;
        }

        location ~* .(png|jpg|jpeg|gif|ico|svg)$ {
            try_files $uri =404;
        }

        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }
    }
}