I have a clematis that grows beautiful leaves and shoots each spring but has yet to bloom with flowers. Last year we had two blooms and the year before none at all.
Certified GKH Gardening Expert
It likely has too much nitrogen. It makes the plant grow lush but with few flowers. Try adding bone meal. This will add phosphorous and balance out the nitrogen. Also, if there is lawn nearby that you fertilize, try not to do it near the clematis.
Here are some other possibilities: