GNOME Display broken

i am working on RHEL 7 on vmware.. tomorrow i am working with ipa in this machine.. from today ,whenever i run this machine or restart it ,this machine take much time to show (approximately 3-5 minutes) login display. suddenly ,GNOME Desktop is not available/ after open this machine it load graphical environment ,but not shows login screen. loading for while,it shows non-graphical environment/cmd-based environment. i also try to install gnome desktop with yum groups install "GNOME Desktop"-y .it shows that ,no packages available... how can i bring back my gnome display ???