There are several things that can cause a Bird of Paradise plant not to flower, including diseases and pests. The plant is susceptible to spider mites and mealy bugs.
When the bugs begin eating away at the plant, it can cause the leaves to die off and prevent the plant from blooming properly. Leaf spot is a disease that is common in Birds of Paradise plants. This disease is caused by fungus or bacteria. If the disease is left untreated, it can cause the plant to die and prevent it from flowering. Since the plants need adequate sunlight, they very rarely flower when kept indoors.