Troubleshooting Connectivity Issues with Older RDS PostgreSQL Instances

Hello AWS Community,

I'm encountering a connectivity problem with my RDS PostgreSQL instances. These instances have been running for years without issues, but now I'm experiencing timeouts when trying to connect to them from outside AWS.

• Two instances are configured as public with correct VPC and Security Group settings.
• I've reviewed all configurations, restarted the instances, and tried connections from different sources.
• Interestingly, I created a new RDS instance with the same settings, and it connects fine, but the older ones don't.

I'm seeking guidance to troubleshoot and resolve this issue with the older RDS PostgreSQL instances.

Any insights are appreciated.

Thank you,