Have you kept watered?

Any shrub or, in this case, climber, planted in spring will unfortunately need to be kept well watered - we're talking a couple of gallons a week at least for a tree, maybe a bit less for smaller plants, applied directly at the base of the plant. Even if it rains, unless the rain is torrential or goes on for hours, it doesn't get down to the bottom of the rootball (usually a good 6 inches), so the plant is entirely reliant on you keeping it going till autumn, until its established a larger root system out further into the ground.

Leave the hose trickling at the base for a couple of hours, or water with a few gallons now.