Strelitzias are exotic plants that were first brought to Europe by the botanically savvy explorers of the late 18th century. Why your strelitzia (bird of paradise flower) does not bloom, we can only guess from a distance. Probably your Strelitzia has stood too warm or/and too dark, because for the plant to bloom reliably, it needs a bright winter quarters at temperatures around 10°C. During this time, watering should also be sparing.
The strelitzia should stand in the summer sunny and protected from the wind. Young plants also tolerate the blazing midday sun, but should be gradually accustomed to it. During the growth phase, the plant needs warmth and plenty of light. The water requirement of the strelitzia is strongly dependent on the number of leaves and can be described as quite high, as a lot of water is evaporated through the large leaf surfaces. It must be watered regularly and fertilized until August (about every two weeks).
In winter, the substrate should be kept only very slightly moist, especially if the winter is cool. Then the strelitzia also wants to stand as brightly as possible. Strelitzias need a bright and cool winter quarters with temperatures of 5-12°C for dormancy in winter. Then they are really kept only moderately moist.
But: If the plant winters warm, it needs more water and the warmer the wintering, the more light must be available. Too much heat is at the expense of flowering in the summer, so it is best to keep really cool, light and little watering.