Hi Elaine and welcome to GoY. Clematis pruning depends on when they flower… presumably your clematis did flower in the past so can you tell us when. If you happen to know which variety it is even better...

early flowering before april are usually pruned after flowering. Summer ones usually in the spring just to get them in shape/under control. Winter flowering ones again as and when, usually late spring early summer.

Need to know the variety - if its a viticella group one (such as Jackmanii) they should have been cut back to 2 buds from the ground by mid February. All the other groups don't need this treatment.