The reasons for no flowers on Wisteria are complex, but Campsis are simpler. Lack of flowers there can be traced to either not enough direct sun, or too frequent pruning. Campsis needs a minimum of 6 hours of direct sun a day to form flower buds. Since the flowers form on the tips of the growing branches, if you are having to chop it back several times a year to control size--or just to "keep it neat"--the growing tips may not be in existence long enough to form buds. Proper pruning for Campsis involves a severe cutting back in early spring, just before it starts to sprout. High nitrogen fertilizer may result in fewer flowers, since the stems will grow longer before blooming, but rarely results in a complete lack.
Lack of bloom on Wisteria can be caused by lack of sun, improper pruning, being too young, too much nitrogen fertilizer, or any combination thereof. Answering that will require a complete history of the vine, and should be answered by someone who has more experience with it than I have.