504 Gateway Time-out issue in EC2 instance

I did all my normal configuration setup on an AWS EC2 instance. I cloned the docker-zulip folder in my ubuntu machine, wrote the mandatory settings in override.compose.yaml file in docker-zulip folder, put my secrets in /opt/zulip/zulip-secrets.env file, made the external host "zulip.library.gwu.edu"and setup my SSL certificates. Still when I try to run the docker by docker compose up, and go to my external host website. All I see is "504 Gateway Time-out". I don't know if it is a docker-zulip setup issue or an AWS configuration issue, but I am not able to solve it. Please help. <img width="1918" height="1061" alt="Image" src="https://github.com/user-attachments/assets/fd3784b1-ef01-465b-a115-2d0034b9f6b7" />