I need to add two more sims to be able to build a sports centre to achieve..

Question for The Sims FreePlay

I need to add two more sims to be able to build a sports centre to achieve the goal of my preteen doing barre exercises. I currently have 10 sims. At first it told me I could not have a new sim because I wasn't at the right level so I got up to level 20 where I was told another sim was unlocked. Now when I go to add a new sim, it tells me I have to wait until my new sim has arrived before I can add another one. I am not currently building anything and have no babies on the go. So what does it mean by arrived? If I press on the crib I have then it says I can have a baby, by the way, but I've already had one and don't want more!