Into the Future/World Adventures - Sim Disappears Upon Arrival

Previously, I have been able to play both Into the Future and World Adventures but for whatever reason, that is no longer the case. World Adventures has been unavailable to me for some time but now I'm having the same issue with Into the Future; upon arriving at my destination, my Sim's portrait and need bar are empty--as if I didn't have a Sim. I have tried other people's suggestions of making various copies of my game, editing the travel destination, choosing another household, etc. and nothing has worked. Strangely, I only have this issue with my current major game, not with another one that I barely play. I have no custom content and no mods so there is definitely no corruption from an outside source. I can still play the game, which is great, but at this point those two expansion packs (maybe three...I haven't checked University yet) are looking like a waste of money. Any help would be extremely appreciated. Thanks!