So I have a fairy toddler and I'm trying to age her up via "Trigger Age Transition" ( Birthday cakes NEVER work for me ) and it says " It's Violet's birthday! " but she never ages up. Instead, she walks off to play with a toy. So I shift click and click "Edit sim in CAS " and it shows the loading screen, but it never opens! I have no mods, and a handful of CAS CC (mainly hair ) and I only save right before I quit and I just gave the rest of my family a makeover! It'll take forever to do it all again ( I've done this 3 times already, thanks Violet ) Maybe I don't age her up, and just open CAS and age her up there? Please help!

Update: I think I solved it, but you guys are still welcome to add your input, because I read it all.

I would suspect that whatever is interfering with birthday cakes might be causing your issue. I can't see how hair or clothing would be an issue, but considering that it's hard to immediately see what a refrigerator has to do with giving gifts it would be worth making a backup of the save and then seeing if removing your CC and clearing the caches helps.

Where you are not using any mods they obviously can be ruled out as the cause of your problem. Try what Ghost sdoj suggested and see if that helps. Often some CC items can become corrupt for one reason or another. If removing the cc does not help it would be helpful if you provided some detail such as your patch level, Mac Or PC, system specs.

In the meantime, if I may I'd like to offer some additional suggestions:
I do not want to push mods on you if you prefer not to use them. Many, if not most S3 players these days have found they can not maintain a clean healthy game without them.

The following basic mods will clean up your game after a few reloads, provide error reporting that more often than not identify in game problems such as the one you are experiencing now.

NRaas Overwatch Overwatch has clean ups once a day (3 am) to get rid of unnecessary/obsolete object codes and recovers stuck Sims more better than the EA way. There are also a lot of silence checks the mod does, if certain things goes out of wack (corrupt outfit, stuck in aging, fixes genealogy, etc). Any Script Errors generated can upload over at NRaas for further examination.

NRaas Error Trap also cleans up your saves of obsolete things when you load up your game. Catch any errors caused by the game core or any mods that runs on the background that otherwise goes silently by, it will produce ScriptErrors that you then can upload over at NRaas for further examination.

NRaas Master Controller has a variety of game options available including the ability to reset a sim, lots and/or a complete world. Doing so often corrects in game play issues similar to what you are currently experiencing. MC also generates script errors.

If you need help with any of these there are plenty of members right here at MTS who are experienced with the NRaas Suite or you can post right over at NRaas.

Another step to consider going forward: only saving before you quit a game leaves you with no option to go back in game to a point where the game was working. It also makes it difficult to identify at what point the problem started. Doing a "Save As" frequently, especially during lengthy in game play where your sims and world have advanced or working in CAS and/or Edit Town.

Okay thanks! I think I found the problem though. I placed down a house from TSR and after I moved my family, the toddler wouldn't age up.
I'm not sure about mods yet because I'm still new to The Sims 3 and it's something I may consider, but I don't want a lot of lag on my game. I'm going to go through my CC and remove what I deem unessacary and see if that clears things up a bit. Thanks so much guys <3