Sometimes while you are launching games from Steam, Steam Cloud sync error can appear.
This error means that Steam failed to synchronize local files with the Steam Cloud servers.
If you have an error like this, either Steam failed to sync your files before closing, or an older version of your game data was uploaded to the server because of the sync.
The new files are probably still on your previous computer, but have not been uploaded to the server.
Please restart your game session and see if your game data is synchronized. Generally, restarting Steam helps to resolve this error.