@lexileeann05
I suggest you try a user folder reset first. Just rename the "The Sims 4" folder to something else or move it somewhere safe outside the "Electronic Arts" folder. Then start the game and create a new save. Check to see if the issue is still there when you make the new sim. I'd suggest you make at least one of each age. Once you've made the new sims and placed them, play them for a few minutes to see if they are visible. Then save and quit.
If you find all the sims and the things you noticed that were broken before aren't anymore, then you'll need to check your old save to see if the problem is still there. So, copy your save from the old "The Sims 4" folder to the new one. Start the game and see if the problem is still there. Don't save when you quit. If at this point, everything looks as it should, then your issue is either an outdated mod or broken CC which you'll have to hunt down and either update, replace or remove.
Hope this helps.