Add the AddTrustExternalCARoot.crt certificate as
Trusted Roots:
Then attach each certificate in turn to your website's Key
Pair in the following order. At this point your Key Pair will be
black.: Yourdomain.crt
AddTrustExternalCARoot.crt
UTNAddTrustServerCA.crt
Your Key Pair will turn now be green.
Once completed, you MUST delete the
AddTrustExternalCARoot.crt
Ensure AddTrustExternalCARoot.crt remains in the Trusted Root area.
Stop and Start the server, your site can now be found
using the https entry