Hi nitu274,
Welcome to Apple Support Communities. We understand that you're having an issue with an online game you're playing. We'd like to help.
Is this game an app you downloaded from the App Store or is it one you play on a web browser? If it's an app, these steps can help you get this issue resolved:
If an app unexpectedly quits, stops responding, or won’t open
If it's a web browser, does this happen on all browsers or just the one you're using? If it's just the one, which browser are you using? Are you able to view other sites successfully on that browser?
Let us know if you need more help!