Hi,
First of all, you must be a member of either Enterprise Admins or Domain Admins in the forest root domain in order to install an Enterprise CA.
Or you can check if the same issue as the following one:
https://social.technet.microsoft.com/Forums/Windows/en-US/fc51410d-46db-4df9-a9c8-b67af4eea888/active-directory-certificate-services-post-config-issue?forum=winserversecurity
If still can't find the reason, you can check out the c:\windows\certocm.log file. It will give you details on what went wrong .
Best Regards,