Connecting to free AWS RDS instance

I'm inexperienced with AWS but in the past have successfully started RDS instances, but that was some time ago (before default security was made more complicated). Now I'm trying a free tier MySQL db. I have made multiple attempts, but even with the most basic (all defaults), I'm unable to connect at all using any tools. I also can't ping the instance.

The default VPC had two routing table entries, as it is supposed to (one for the subnet and one for all other traffic, to go to the internet gateway), and my RDS instance is in this VPC. The default security group allows all ports inbound.

I have included a reference to the SSL CA pem file in the connection request, that was downloaded from Amazon.

Is there anything else I need to do? What am I missing?

If one of you could tell me how to create just the simplest default free DB with no security (this is just for a POC), I will be eternally in your debt.