Make sure your game has the latest version.
Please see the steps on how to get the latest game updates from the links below:
Android: http://zynga.my/UpdateAndroid
Windows Phone: http://zynga.my/FV2CEWindowsPhone
Windows 10 PC/Laptop: http://zynga.my/1SNChxW
In case you're still getting the offline error message, please try the following steps below:
Android: http://zynga.my/FV2CEAndroid
Kindle: http://zynga.my/FV2CEKindleFire
Windows Phone: http://zynga.my/FV2CEWindowsPhone
Windows 10 PC/Laptop: http://zynga.my/1SNChxW