I have had my wisteria (planted in a combination of hard "dirt" covered by 5-6 inches of top soil) for twelve or so years and in the first three or four years it bloomed regularly, such that the neighbors came to take pictures of it!
For the past five or six years, it has had virtually no blooms on it. I have fertilized it with balanced fertilizer. I have pruned it after blooming (what few blooms it had). I have pruned it in late spring before budding out. I have left it alone and not pruned it. I have pruned it severely. I have lightly pruned it. What is going on?