It is not on by default.
Please check this whitepaper for details:
https://technet.microsoft.com/en-us/library/ff955845(v=ws.10).aspx
You probably have missed:
- LDAP referrals
- Publication of the CA certificates in the resource forest
- Inclusion of the issuing CA computer accounts in the Cert Publishers group
- Verification that the URLs in the CDP/AIA are accessible from the resource forest
- Permissions are configured to enable Read and Enroll permissions for groups in the Resource forest
Brian