No certificate templates could be found. You do not have permission to request a certificate from this CA, or an error occurred while accessing the Active Directory.

When trying to access the certsrv page to issue a certificate from a .req or .csr file you are presented the following error:

Now what...
One possibility could be that the Authentication settings in IIS on both CertEnroll & CertSrv has been changed to Anonymous Authentication Enabled & Windows Authentication Disabled.

Change it back to the default which are Anonymous Authentication Disabled & Windows Authentication Enabled and try again.

If the page still doesn't show the templates, you need to check the template version.

When duplicating a template, you are asked what version to make it and given an option of "Windows Server 2003" or "Windows Server 2008".

The certsrv web site is only compatible with the Windows Server 2003 based templates which I think corresponds to version 2. Ironically, this same limitation is present all the way through Windows Server 2012 R2. The certsrv site still can't use version 3 templates. Here's the related KB article:

https://docs.microsoft.com/en-US/troubleshoot/windows-server/identity/cng-templates-not-appear-certificate-web-enrollment