Hi Avinashi,
What selintra is saying is that your problem is due to an incorrect communication between the GUI interface and your server. He gave you some code that will regenerate several configuration files in your server and restart it. It should solve the problem.
To enter these commands, you will have to use the keyboard and screen connected to your server (if you have none, I'll give you another way below). Log on your server with "root" (if you have the console menu displayed rather than the login prompt, just press CTRL+ALT+F2). The password is the same as the one you are using with server-manager.
Then, you obtain a command-line prompt finishing by #. Just type the commands given by selintra. The first one is a little long to execute, and the second one will reboot the server. After that, your problem should be solved.
If you don't have screen and keyboard on the server, you can do it remotely with putty that will give you a remote console of your server. Download and install putty on any client computer using windows. You can get putty on
the official site. Then, you'll just have to give the server's IP address to obtain a console with the logging prompt where you'll have to log as "root" and do as explained above.