DISC AUTHENTICATION FAILURE: NO GAME DISC FOUND! PLEASE INSERT THE SIMS 3 ISLAND PARADISE GAME etc..

I turned on sims like I normally do, but it says: DISC AUTHENTICATION FAILURE: NO GAME DISC FOUND! PLEASE INSERT THE SIMS 3 ISLAND PARADISE GAME DISC BEFORE PROCEEDING. The game disc is in and is recognized by disc utility. It is also not appearing on the the desktop. :? Help to fix it?