The way you teach a horse to jump, is to put a wooden pole on the ground and walk over it, allow horse to check out the pole if it wants. It learns that if it hits the pole with its foot or steps on it, there is a clunking noise and it's nicer to step over.
Once pole on the ground is "mastered", raise the pole slightly off the ground - eg one brick high - so horse has to pay attention and pick its feet up a little more. Walking, then trotting...
Once that step is mastered - raise the pole some more.
I'm guessing you could teach a dog to jump the same way. Teaching a dog to jump on the couch would be slightly different - ie you'd have to start with a platform that was big enough to hold the entire dog comfortably, with maybe a big cushion or pillow on top - and arranged so nothing slips or pulls off. Teach dog to park on the platform, gradually raise the platform until the dog has to jump on it.
With clicker shaping - you'd break it all down into tiny steps - like looking at the platform, touching the platform, putting a paw on the platform.... but a food treat in the middle of the platform might help skip a few steps. And the platform would have to start close to the ground.
It could be that the dog had an unfortunate memory of a fall or similar associated with jumping. My puppy dog at 12 months has decided jumping things under head high - or even head level is great fun. Unfortunately this means the fence between my place and the neighbours and out to freedom down the street, or jumping into the cricket pitch area - and back out. She's happy to jump a rope or a wide band of orange tape/matting. Sigh.
And now I have to teach her to jump in the car, but I'm thinking a ramp might be easier. Since jumping onto a landcruiser back seat almost certainly means headbutting the back of the front passenger seat on the way up. I guess I could get a small platform. One of our arthritic doggy friends uses an old card table with the legs cut down to make a step platform about 8 to 12 inches off the ground (it's slightly sloped), and this enables her to get in the back of a normal station wagon.