对nginx后面的Node.js应用程序的POST请求无法通过

Question

对http://mysite.io:5003/GetProjects的POST请求，工作正常（http）。但是对https://mysite.io:5003/GetProjects的POST请求在我的网站http://mysite.io/Projects上返回Postman中的“无法获得任何响应”和“ERR_CONNECTION_REFUSED”。我正在使用PM2来运行我的backend.js，我也只是运行节点backend.js来调试。操作系统是EC2实例中的Ubuntu 16.04，其端口443处于打开状态。

nginx配置是：

server {
  listen 443 ssl;
  server_name mysite.io www.mysite.io;

  root /var/www/html/mysite-service/build;

  location / {
proxy_set_header X-Forwarded-Proto $scheme;
    try_files $uri /index.html;
  }

    ssl_certificate /etc/letsencrypt/live/mysite.io/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/mysite.io/privkey.pem; # managed by Certbot
    include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
    ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}