@jatinkhanna, can you verify that you’ve implemented the RHSM Plug-in (Red Hat) version 18.104.22.168 in the Manage Download Plug-ins dashboard? Also, do you have both the entitlement and identity certificates (i.e. .pem files) located under the following path?
(DRIVE):\BigFix Enterprise\BES Server\DownloadPlugins\RHSMProtocol\certs\cert_set_1
These certs would come directly from the RHEL access portal.