2019 Sims 4 CAS Sims not saving to Library!

Hey got the same problem although I personally use no cc or mods, but the family I had just created didn’t appear in the manage household, started being pretty pissed and researched it and found your question. I actually ended up going in Open the gallery and it was there. Just had to click on my family and at the bottom right, click the option to place in the world.

hope this helps someone out there!