Sims 3 Toddler won't age up

@kittyclaw1980  I've split your comment into its own thread because the previous thread was quite old, and it clearly didn't help.  (Also, the official Sims forums were moved and reorganized years ago, so none of the old links work.)

There are a few different methods you can try; feel free to skip any steps that haven't worked.

• Age your sim up manually with a cake.
• Age the sim through testingcheats.  Bring up the cheats console (crtl-shift-c) and enter "testingcheatsenabled true" without quotes, and then shift-click on the sim to see the option to "trigger age transition."  Be sure to turn off the cheat ("testingcheatsenabled false") when you're done.
• Use testingcheats to bring the sim into CAS, and reassign all the outfits.  Sometimes a custom content item can prevent a sim from aging up properly, so it's best to change everything to vanilla (non-cc) content.
• I believe what the old post recommended, although I could be wrong, is to go into game options and extend the toddler age range by one day, then turn aging off, then quit.  Then reload the game, turn aging back on, and see if you can force the age transition.  But I'm not sure whether this would work.
• Evict the family from their house in Edit Town, and move them back in.  They'll keep their jobs and relationships but lose their promised wishes and opportunities.

Each time you try one of these steps and it doesn't work, quit to desktop and delete your cache files (in your game folder in Documents) before reloading.  Delete the cache files as a first step as well.  These files can fill up with stale data and should be cleared regularly even in the absence of game issues.  For reference, the files are:

• CASPartCache.package
• compositorCache.package
• scriptCache.package
• simCompositorCache.package
• socialCache.package