Wordpress on EC2 responds an error "this site can't be reached"

Hi all, I have been trying out EC2 services with my hobby Wordpress website. It had been working on t2.micro instance for 4 months. But since yesterday, I cannot reach it. However the instance seems up and did not go down at all (up for 121 days). I did not change any of the important configurations, like Route 53 or EC2 configs. When I analyze the auth.log, I have seen that there are many invalid user logs which are totally unrelated to my instance IP. Could you help me to find out what is the problem under this unreachability issue? Thank you all.

Additional info: I looked at AMIs under Images on EC2 page. There seems nothing. When I was installing the website on EC2, I did use Wordpress by Bitnami AMI for sure. Can it be the problem?