We have had a beautiful flowering white Wisteria for about 15 years on a roof terrace planted in a very large built in planter with other plants. This year the buds came out for the blossom and the leaves and then they just stopped. They are still like that today, although some of them are starting to fall off. There were some cobwebs on the buds and ends of the plants
and I sprayed these with bug clear. They have now disappeared. The planter is full of roots; however, all the other plants are thriving.
Certified GKH Gardening Expert
It sounds like you may have a mite problem, most likely spider mites. Not all insecticides will treat mites, so make sure that what you are using to spray the plant contains a miticide.
This article will help you learn more about spider mites: