the potato vine may well be dead -if there's no signs of life from the passion flower, bear in mind everything's late this year - check the plant back to the base to see if there's any green anywhere - if there is, cut back to that.
As for the clematis, it is unlikely to have been killed by the winter, unless it was in a pot. Again, check at the base for signs of budding or growth. You don't say which clematis it is, so its possible its one that should have been pruned right back to the bottom in February.