What's the problem? Why can't you start the game? Do you have an error message? Did you try to udpate the game but encounter a problem as result? In such a case, a fresh download of the game and moving your save files would be the quickest way to make sure that all game files are okay.
If you want to update and you have an older version, download the full game again and copy&paste the entire content of the www/save folder to the same location in the new game folder. Only use the "update files only" when you have the previous update, since they contain only the files that have been changed since the last update. I made a video about both options here: