I can't see name bars anymore.

I don't know if anyone asked or told this but I couldn't find it on the internet. Idk why it happens but I can't see the names of my sims above their heads anymore. 

When the game just loaded and I restarted it or started playing it they will show but after a while they will disappear. Idk what to do, can someone help me?

Sorry for my english, it isn't my first language.