Gokul,
It appears that you are using the freeware edition (the free download from the
www.electronicsworkbench.com website). This version is only a 45 day free trial and in order for it simulate it must connect to our server. Without a proper network connection, unfortunately the simulation feature will not function correctly, and this is the reason for the 'Simulate' menu not being available.
If your network connection is being hindered by a Proxy Server allow for the proxy server. If it is still not working, please contact your local distributor or sales department. They might be able to help you.