正如Sanoj提到的，您可能添加了错误的端口。502 Bad Gateway error意味着NginX无法连接到MI服务器。因此，请检查您是否可以连接到NginX运行的所有MI示例。您可以使用telnet或curl等工具进行测试。这将确保您没有任何连接问题，如防火墙规则阻止连接。
This解释了所有使用的端口以及如何更改它们。
This是MI的NginX配置的官方文档。（似乎这里的一些端口也不正确）以下是带有正确端口的NginX配置示例。

upstream wso2.ei.com {
server xxx.xxx.xxx.xx1:8290;
server xxx.xxx.xxx.xx2:8290;
}
server {
listen 80;
server_name ei.wso2.com;
location / {
        proxy_set_header X-Forwarded-Host $host;
        proxy_set_header X-Forwarded-Server $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_read_timeout 5m;
        proxy_send_timeout 5m;
        proxy_pass http://wso2.ei.com;
        proxy_http_version 1.1;
  proxy_set_header Upgrade $http_upgrade;
  proxy_set_header Connection "upgrade";
   }
    }

upstream ssl.wso2.ei.com {
server xxx.xxx.xxx.xx1:8253;
server xxx.xxx.xxx.xx2:8253;
ip_hash;
}  
server {
    listen 443;
    server_name ei.wso2.com;
    ssl on;
    ssl_certificate /etc/nginx/ssl/server.crt;
    ssl_certificate_key /etc/nginx/ssl/server.key;
    location / {
        proxy_set_header X-Forwarded-Host $host;
        proxy_set_header X-Forwarded-Server $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_read_timeout 5m;
        proxy_send_timeout 5m;
        proxy_pass https://ssl.wso2.ei.com;  
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
            }
        }