How to solve 502 Bad Gateway problem?

[MallemIsmail]

Hi, i did set up NPM docker in my VPS successfully , i set up proxy host to another docker inside my VPS which was accessible via public ip of my VPS X.X.X.X:8888.
And then when i go to domain test.example.com i get 502 Bad Gateway openresty. (I didn't forward it to localhost:8888 i know how docker work but directly to public ip that's already function fine X.X.X.X:8888)

To debug this problem i tried to curl test.example.com inside NPM docker i get
curl: (7) Failed to connect to test.example.com port 80: Connection timed out
Same goes if i test X.X.X.X:8888 if i curl any other website it work.

Host OS is debian 10 i used the default docker compose provided in NPM website.