Nginx + NodeJS Express API服务的React应用= ERR_CONNECTION_TIMED_OUT

Question

我让React App带有Nginx和使用pm2运行的NodeJS Express Backend API。昨晚一切正常，但是今天当我访问该网站时，发送到API的每个请求都返回ERR_CONNECTION_TIMED_OUT。

当我尝试使用API Tester测试API时，一切正常。

我的nginx配置：

server {

    root /var/www/[my_repo]/client/build;

    index index.html index.htm;

    server_name www.mydomain.com mydomain.com;

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


    listen [::]:443 ssl ipv6only=on; # managed by Certbot
    listen 443 ssl; # managed by Certbot
    ssl_certificate /etc/letsencrypt/live/mydomain.com/fullchain.pem; # managed by Certbot
    ssl_certificate_key /etc/letsencrypt/live/mydomain.com/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
}

我网站上的

DevTools： enter image description here

API测试器（相同的URL）： enter image description here

顺便说一句，为什么当它是GET请求时，在DevTools中为什么显示OPTIONS url ..？ 谢谢！