Gah,... Ok, I'm at a loss. I can't connect to my local box endpoint for alexa-skill testing and keep getting "the remote endpoint could not be called or the response it returned was invalid" error.
I'm running Centos 7, httpd 2.4.6 (I have added ServerName/ServerAlias to the config), followed the OpenSSL instructions to create a self-assigned cert, port forwarding via 443 is working fine, I can connect via IP and https address. I've tested the SSL cert and everything checks out except for the security warning for self-assigned certs. I tested it using an ngrok tunnel between my box and amazon, and I can access the app through alexa perfectly. It seems to be something to do with the SSL cert, but I don't know what else to test? I also verified the SAN matches. Any ideas?