To prevent the "out-of-sync with the servers" error message only play the game on one device at once.
The error message "Error: Your game is out-of-sync with the servers. You will need to restart the game" may appear if you have Gems of War open on more than one device, such as on your smartphone as well as a computer. This error may also appear if you're attempting to hack the game in some cases or if you have a bad internet connection. For general connection troubleshooting, go here: Connection issues troubleshooting.
If you lost a battle due to this Out-of-sync error appearing you can contact us here. Provide a screenshot of the error message and the exact date, time, and game-mode this occurred and we can investigate the issue! Unless of course, you were hacking the game when this error appeared - then you probably don't want to contact us.