What should I do?

My Orchids don't flower.

Assuming the plants are old enough to flower and/or did flower in the past and the growing conditions (light, temperature & humidity, etc.) are right, try the following. About six month before their flowering, stop using Nitrogen (N). Fertilize your plants using P: K containing fertilizers (N:P:K = 0:10:10). Phosphorus & Potassium induce/promote flowering, Nitrogen induces only new growth. When the “flower buds” appear, return to your standard fertilizing procedure, use N: P: K again. Some orchids flower best under this regime, especially soft-cane Dendrobiums.