Authorize.net requires HTTPS with valid SSL certificate and static IP. Please check with your host to ensure HTTPS is setup and working as necessary. This won't work on shared hosting packages as usually the cert is shared between all domains on that server and will always give invalid domain error. Details for your host as follows.
www.endodonticacademy.org
uses an invalid security certificate.
The certificate is only valid for the following names:
*.bluehost.com , bluehost.com
(Error code: ssl_error_bad_cert_domain)