amazon rds – Why is AWS RDS connections timing out even though it is configured to accept connections?

Hello, I have a PostgresSQL database on AWS RDS, which is located in VPC. His security groups accept Postgres connections on port 5432 from my EC2 web servers residing in the same VPC, and the aws-rds console always shows 0 connections.

Sometimes it shows 1 connection, and when I try to remove and add IP addresses in the security group, 0 connections are restored and will not change after that, no matter what changes I make in the security group. what am I doing wrong here?