You have to enable the Roots chaining certificate, therefore you should add the following line to the "httpd.conf" file in "mod_ssl global module settings" :

SSLCertificateChainFile {PATH to reach the file}/secureroots.crt
* For Apache version 2, use the parameter SSLCACertificateFile in place of SSLCertificateChainFile

where secureroots.crt is the file that contains the chain (Base 64 encoded):

You Certificate must be referenced in SSLCertificateFile.
Your private key must be referenced in SSLCertificateKeyFile.

All other SSL references must be disabled.