I get this when I go to a subsite using https. It exists as a subfolder under the main site. If I call it as a subfolder, it is fine. What setting am I missing in the certificate setup (this is a paid cert)?
Is this related to the API connectivity issues you were indicating on API Requests Made With TLS 1.0? If so, I'd recommend continuing the discussion in only one of these threads so to avoid any confusion from other members reading and trying to help out in a solution.
If this is unrelated, I think a little more detail about how the error is being encountered would help others familiar with the issue offer a suggestion on how to resolve this.
From the looks of it, your trying to establish an 'https' connection through a name your currently installed SSL certificate is not issued for. This is why connections through www.paganalliancechurch.org work but not donate.paganalliancechurch.org. You can see the accepted Common Name and SANs identified in an SSLShopper check here.