Not able to install `devtooldset` package on RHEL 6 system when having `1-year Unsupported Red Hat Advanced Partner Subscription`

Issue

• Why shows No Matches found message for devtooldset package when system is subscribed to rhel-server-dts-6-rhb-rpms repository ?

• The yum repolist shows below channel which provides devtoolset packages but still yum search shows No Matches found,

"rhel-server-dts-6-rhb-rpms                   Red Hat Developer Toolset RHB RPMs for Red Hat Enterprise Linux 6 Server enabled:"