My files work under localhost, but when I put them through EC2 t2.micro instance, the connection is denied.

As the title suggests, my files work under localhost. I've checked that there is no problem in the code. Yesterday, I changed the billing information, so I thought the card payment being unable to be processed was the reason why AWS stopped opening the server. But, I noticed that AWS charged me with the new card yesterday.

I don't know how to fix this problem. Localhost works fine, yet the public IP wouldn't work. I keep getting "ERR_CONNECTION_REFUSED". Should I buy new instance?