It takes this plant 6 to 7 years to grow mature enough to bloom so I suspect the problem may be not enough cool winter days and sunlight in your climate. I have seen Bird of Paradise flower in the very cloudy climate of Aberdeen Washington so the amount of full sun days is not as important as a keeping it cool in winter between 55 and 60 degrees and letting the soil dry out between watering. This is one houseplant that needs to be kept dry in the winter so that it will go dormant. Water just enough to keep it from wilting during the winter months  and keep near window or sun room so it can experience the days becoming longer in the spring. The indoor Bird of Paradise (Strelitzia is Botanical name) will flower in the spring after winter rest. I suggest an application of Osmocote Plus granules in the spring as soon as you see signs of new growth.  Hoping with these tips you enjoy some tropical delight this coming spring. Keep growing, Marianne Binetti