"In the apartment there is a bedroom, a bathroom and a kitchen."
Translation:W mieszkaniu jest sypialnia, łazienka i kuchnia.
I can assure you that we have "są" on the list of accepted answers. Maybe you made a typo somewhere? Your correction then shows the main answer (which uses "jest"), which often can create an impression that your answer was considered wrong, although you actually just had a small mistake somewhere.