TrendMicro on GovCloud

hi, So as you say you can't connect to your DB instance. it could be one of many reasons .

First check your security group associated with your VPC and confirm if the inbound and outbound rules you set allows traffic from your source(local machine or where you connecting from) refer to this link for such issues [1]https://aws.amazon.com/premiumsupport/knowledge-center/rds-cannot-connect/

make sure public accessibility of your Database is set to "YES" (can be done via console)

check the connection between your EC2 and RDS

Security groups of the EC2 and RDS if they allow each other NACL's rules of the EC2 and RDS if they allow each other Routing table of the EC2 and RDS if they allow each other. If the EC2 and RDS are in the same VPC the IGW will not be needed. But if in different VPC it will be

also check connection between EC2 and RDS. From the EC2 you can test connection to RDS by running a linux command: telnet [rds endpoint] [port used] Example telnet testing.casdasdasd.us-east-1.rds.amazonaws.com 5432

feel free to reach out if there's anything you need help with.