Hi, 100 baby challenge player here, had to age up two teens into young adults. I had oldest teen put candles on a chocolate cake (I had one in the fridge) & blow them, and as other people said, the little cake appeared in her action queue, she teleported a bit further away from the cake, and didn't age up. I reseted her, and had her mother put candles on the cake this time. She teleported again, but this time she did age up. I thought that teen couldn't put their candles on their own birthday cakes anymore, so with the youngest sister, I had the mother put the candles on the cake on the first try. Didn't work. She had the pink "age up" cake in her queue for a second, then teleported, but didn't age up. The family celebrated, and had the positive moodlet from the birthday celebration. Of course, I reseted the birthday girl and tried again and again, having different people putting the candles on the cake, putting it on a different counter, and reseting her between each try. I did that for six sim hours. In the end I gave up and used a cheat code to age her up. I still have no idea while it worked with the first one and not the other. They are twins, and it was not their birthday, I just had to age them up and get them out of the house.
Sorry for the long post, I wanted to give as much info as possible, if it can help fix it.
Edit : None of them were self assured, so I doubt that's where it's from.
