Lipstick Vine Has Never Flowered

I received a clipping of lipstick vine three years ago. It has grown quite a bit, but never flowered. How can I get blossoms?

The lipstick vine (Aeschynanthus speciosus) houseplant prefers a bright sunny location, moist soil and high humidity to bloom. It usually requires less water and no fertilizer during the low light conditions of winter. Like most flowering plants it needs to be slightly potbound to bloom. Use a flowering houseplant fertilizer March through November. These fertilizers are higher in phosphorus and encourage plants to flower. Photo: Veli Holopainen