Here are a few things to think about: Is something eating the flower buds before they can flower? How long have you had your plant? Has it had enough time and resources to get established? With some plants, it can take 2-3 years to really put on flowers.
However, the usual suspect is too much nitrogen and not enough phosphorus. Take a look at the fertilizer you are using and the three numbers on the label. The first is nitrogen, the second is phosphorous, and the third is potassium. Annuals and perennials do well with a 10-20-10 balance, or something similar. Be sure to follow label directions on how often you should fertilize and how much to apply. I bet this will solve the problem of no flowers!
Thanks for writing!