Event ID - 27

Event Id27
SourceCertSvc
DescriptionCertificate Services did not start: Hierarchical setup is incomplete. Use the request file %Systemdrive%:\Name of subordinate CA.req to obtain a certificate for this Certificate Server, place it in %Systemdrive%:\Name of subordinate CA.crt, and run the Certificate Server Hierarchy Configuration tool to complete the installation.
Event InformationCAUSE:
This problem can occur if a certificate that is issued by the root CA has not been installed correctly. Even though you can right-click the certificate (which is downloaded from the root CA) and use the Install Certificate option, this method is not the correct method to install a CA certificate. If you use this method, it can cause the error messages that are described in the "Symptoms" section of this article. 
RESOLUTION:
To resolve this problem, you must properly configure the subordinate CA: 
In Administrative Tools in Control Panel, start the Certification Authority tool.
Right-click the name of your subordinate CA.
Under All Tasks, click Install CA Certificate.
Locate the CA certificate file that was downloaded from the root CA.
Click OK.
Reference Links An Event 27 ID Error Message Is Generated When You Set Up a Subordinate Certification Authority

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