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Do you have this issue only with that Words with Friends app ? By reboot do you mean normal restart (turn off and turn on) ?
We can try three basic troubleshooting steps and see if it works or not. First we can reset your iPad and see if it works or not. Press and hold down the Power button and Home button at the same time until it shows the Apple logo. When you see the Apple logo, release the buttons and let it boot. This will soft-reset all hardware components of your iPad.
If that didn't work, then go to Settings > General > Reset and tap Reset All Settings. This will reset some settings like WiFi, bluetooth, wallpaper etc. But you will not lose any files or contents.
Check the game now. If it still not working, then we will have to delete the game and redownoad a fresh copy from App Store. Note, when you do this you will lose all stats and saved data of that game (if any). To delete the game, press and hold down the Word with Friends icon in home screen and it will start wiggling. Tap the x icon on it and it will be deleted. Then go to App Store and redownload the game.
Then check the game. Please let me know if the above solutions doesn't work, so we can troubleshoot further.
Remember, this is not my final answer. If my solutions didn't work please don't rate me bad or poor. Instead please reply back to me and I will continue to help you until we fix the problem or until you are satisfied.