Checking log, it also said it failed to connect to ccp76234.live.dynatrace.com during installation, any idea what else I might try?
Why do you need a certificate?
I am asking because it suggests that you have a SSL termination proxy between the AG host and Dynatrace SaaS cluster. In other case, when you have a direct connection or a regular proxy, you do not need to configure the certificate during installation.
I suppose that you have checked the installer log file. Please check also /var/log/dynatrace/gateway/dynatracegateway.0.0.log or dynatracegateway_Debug.0.0.log, they are more talkative and may give you more hints.