I'm using openVPN to connect to one EC2 instance from another. The client cannot see the server, however, despite that servers outside of AWS can see the server and successfully negotiate with it.
I speculate that this is because UDP isn't configured properly. I've already opened the UDP ports on that instance via the AWS SecurityGroups - this didn't work, both for all incoming UDP, and/or for UDP from the server IP.
Does anyone know what might be misconfigured in AWS to prevent this?