Re: Sims 3 - All my Sims are invisible.

do you have a copy of the family saved to the library  ? as you may need to start a new game they will keep the relantionships they have with each other and whatever items in the inventories but you'll be starting with wishes and building up friendships around the town again

or try the reset all sims cheat in case a sim is stuck that you can't see where they are stuck to reset all sims cheat to reset all sims ctrl+shift+c hold all 3 together in the menu bar that appears at the top of the screen type in resetsim * (inculding the * hit enter ) this will reset all sims inculdeing your own make sure your own aren't doing anything important cancel their acton q   if that works for you then once the sims are visiable save the game with the save as give the save a new name  then save and quit launch the game and see if all as it should be with your new save