If your frangipani tree is taller than 2 metres and has more than 30 crowns, it should be producing many flowers every summer. If it isn’t, it’s probably because it’s not getting enough sun or it’s getting too much water. If you have a not-so-important tree that is blocking the sun, consider removing it or copping it to a smaller size. If you can’t let more sunlight to the frangipani, consider transplanting it to a better position.
If your frangipani is less than 1.5 metres tall and has less than 10 crowns, you should not rush it to produce flowers. Besides flowers looking pretty and smelling nice for humans, flowers are not so beneficial for the frangipani. Flowers use up a lot of energy. Many small frangipanis put their energy into making their roots and branches thicker and stronger which is much better for the long term.
Also, flowers are part of the reproduction system. Seed pods are produced on flower stems after flowering. Please don’t force your frangipani (or anything else) to use its reproductive system until it is developed and mature enough. If a small frangipani flowers, it’s best to take the flowers off as soon as they open or, even better, cut the flower stem off as soon as you can.