Can use IP address (with port, i.e: 204.48.21.23:3000) with postman to call API , but name (from A record) not working.

So, I’m running an angular / spring boot app as containers on a droplet. For some reason, the localhost call through nginx isn’t working ( getting ERR:CONNECTION_REFUSED). However, I was able to call it using my IP : PORT address. But since I need my webserver to make calls to an android app, I decided to set it up as a different droplet (I’m not sure if this is the best way or method, I’m new to all this). So, on cloudflare I have “kronologi.ca —> ipv4” from digital ocean which serves my Web App. This works fine! I see my login page and what not.

Now, the issue is when I create a sub domain and point it to my second droplet with “api --> ipv4” and I call api.kronologi.ca:3000/rest/of/api/call , nothing works. Postman just hangs and the same applies everywhere else. However, calling IPv4:3000/rest/of/api/call works 100% fine. I’m not too sure what . I’m suppose to do or what I’m doing wrong. Is it a set up thing in my droplet?