I know there was a previous thread on here about the same issue but it was marked as fixed so I can no longer respond to it.
I'm currently playing in a legacy save where I aged up my teen into a young adult, I noticed a pop up never came to give him a new trait. At the time I wasn't super worried and I figured I could just go into cas and update him later. Well later when I did finally go into cas it wouldn't even give me the option to give him a trait. It was like he was still a teen and only had two trait options. This sim wasn't my heir so I again wasn't super worried and figured it was just a one time thing. But now I've aged up his brother into a young adult and he's also having the same issue. The sim I'm using for my heir is still a child so I have a little bit until she ages up but now that both of her brothers have had this issue I'm scared she will to and it'll ruin the gameplay idea I had for her.
I play on xbox so obviously no mods but I do own quite a few packs.