You will see a "Resyncing" error (in big Red letters) if your client is out of sync with GFG's server. This occurs when the connection between you and our server was lost.
As a result, you will be able to begin upgrades, train troops, or make other actions within the game, despite your connection to the server already being lost, upon reconnecting to the server (this all done behind the scenes) you will encounter a "Resynching" error and will notice that the actions you attempted to make, were not made. Your account will be in the state that it was before losing connection with the server.
Losing connection to our servers can happen for a variety of reasons, including, but not limited to: poor Internet connection, server issues, ISP errors (and maintenance) and/or device performance.
We are sorry for any inconvenience that this causes.