Upgraded MySQL and accepted SSL/TLS Certs and now connection refused.

Question

I have an active VPC Peering connection between 2 accounts where an EC2 instance on 1 account can connect to and use a RDS MySQL instance in the other. This has been working fine until I did 2 things and I'm not sure what the problem could now be.  
When trying to connect to the RDS DB from the EC2 instance I now get this error:  
ERROR 2003 (HY000): Can't connect to MySQL server on ......  
The 2 actions I took lately where to upgrade the DB to 5.8.16 and accept and implement the update to Amazon RDS SSL/TLS certificates.  
Does VPC Peering use SSL/TLS in a way that the change of these certs on the DB could be messing things up?

Answer

Did you update the EC2 instances to use the new certificate bundles? You have to do this, in addition to updating the RDS instances, for connectivity to work (assuming you use SSL/TLS to connect).  
  
https://aws.amazon.com/blogs/database/amazon-rds-customers-update-your-ssl-tls-certificates-by-february-5-2020/

Upgraded MySQL and accepted SSL/TLS Certs and now connection refused.

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