Repairing the GameIn Origin > Games Library tab: Right-click on Sims 4 or Sims 3 and select Repair. (Click image to enlarge)
It only affects the install files for the actual game. It does not make any changes to the saved game files. Meaning that your saved games are safe, they won't be deleted. If you have any mods in the game, you may want to remove the mods folder first before running the repair tool.
Essentially, it compares your installed game files with the files on the Origin server and re-downloads any files that are different. It will also repair registry entries for the game if any have been altered or erased.
Note: This post has been locked as it's for informational purposes.