My sim was hungry while managing her restaurant. Her whole family came to hang out/help/do homework etc. When my sim tried to cook dinner on a stove in the back room, her sister said that it was inappropriate behavior. After a few more tries to complete the meal, my sim was asked to leave. At that point, I lost control of all of my sims. The restaurant, while it remained opened, was inaccessible. I could not raise or lower the walls or look inside except through the windows.
My sim was able to cook a meal the night before but she was the only one in the household at the restaurant. No one was there to tell her that her behavior was inappropriate. I will reload my game and try again. Perhaps if I give her the "Always Welcome" trait, she will be able to cook herself dinner in her own restaurant while her family members are on site.