Web references:

http://social.technet.microsoft.com/wiki/contents/articles/7734.certificate-enrollment-web-services-in-active-directory-certificate-services.aspx

Certificate Enrollment web services – access was denied by the remote endpoint:

http://msitpros.com/?p=1930

https://social.technet.microsoft.com/Forums/windowsserver/en-US/809459c7-e090-48d2-bdff-ab42b3ba8270/certificate-web-enrollment-policy-service-access-was-denied-by-the-remote-endpoint-0x803d0005?forum=winserversecurity