membership 2 secure connection problem

I am trying to get ready to launch my membership site in the next 2 weeks…

In testing the payments, I am getting an error page that says “Your connection is not private

Attackers might be trying to steal your information from (for example, passwords, messages, or credit cards). NET::ERR_CERT_COMMON_NAME_INVALID

I have checked and the api keys do not seems to have any spaces before or after.

The test page is here

Do I need an SSL certificate? Is that what’s going on?

Thanks a bunch!