Can't access Oracle Cloud Always Free Compute http port

Yesterday, I was set up my first always free compute VM. I installed ubuntu 18.04 minimal on my VM. For my web service need, I installed Nginx. I'm confused because when I tried to access my public IP via a web browser, the Nginx welcome page didn't load. I think that is because port 80 didn't open. So, I tried to open that with set Ingress Rules in Security List Details menu as the picture below. [Ingress Rule for port 80][1] [1]: https://i.sstatic.net/aHid4.png But now, I still can't access the web server in my VM. May be there more experienced people in Oracle Cloud who can help me to solve this. Thank you