Try playing mind games, pick him up and drop him half the stairs and lower and lower each time to the point you just pick him up and drop him at the same place. Each time he get up some part on his own reward it... Or like stated earlier try to get him going with a toy and use that to get him up the stairs while playing like fetch, throw it a few stairs up then higher and higher.
Anything's possible, but as mentioned, he has no issue jumping up and down from the couch multiple times per day. In fact, one of the games we play is that (while he is sitting with me) I throw his toy across the room into another chair. He jumps off my chair, runs over to the other chair, jumps up to retrieve the toy, then jumps down, runs back to my chair and jumps back up to bring it to me. He loves this and will do it all night if I would.
if it be the case it would be jumping down the issue or going down the stairs not going up... any dog and jumping down is not a good combo, I try to limit that with my dogs... there's a easy way to tell, slide your thumbs on his spine, vertebra at a time if you feel him tensing up at one he his in pain and most likely is a calcified disk but he his pretty young for that at 2 years old.
Our shepherd experienced stairs for the first time when we moved into a fifth wheel camper. She also has arthritis in one hip.
She just needed moral support until she built up her confidence 
It's only 3 risers. If I put him in the middle, it's a crap shoot whether he goes down or back up. If we're at the top and I put his front paws on the middle, he goes back up. If we're at the bottom and I put his front paws on the first riser, he goes all the way up.
I am seriously considering installing ramps....
Are you over feeding the pooch at meals???
He gets 1/4 cup (1/8 oz) Science Diet about 430 AM and the same thing at 330 PM. One small Milk Bone chewy treat about lunch time. Acts like he's starving at meal times.
I dump at least 4 to 6 of the big coffee cans (1 1/2 pound or so) into 3 bowls for our pack. They share those and eat when they can depending on status and what they want. Puppies are slowing down at a year old. They were good for 4 cans by themselves during the latest growing phase.Well, you Sir are well trained.
We tried the hugs ,back patting and kiss routine as everyone arrives and leaves (we would do
Is there room for a ramp? I put one in for my MIL, covering 50% of the stairs. Both dogs would take the ramp going up and take the stairs going down. I never figured out why....It's only 3 risers. If I put him in the middle, it's a crap shoot whether he goes down or back up. If we're at the top and I put his front paws on the middle, he goes back up. If we're at the bottom and I put his front paws on the first riser, he goes all the way up.
So far, the toys and treats don't work.
If we can EVER get him to do the 3-riser stairs, THEN we'll start working on the 5-riser stairs to get into our hi-boy bed.
I went with a ceramic ball in our rescue dog's bowl. Slowed him down a little. It's softball size. Labs will eat until they pop....
why this feel like a condescending comment? yes positive reinforcement goes a long way and is one of the building blocks of training but not the only one and certain things are easer to trained then others … things like separation anxiety, hoarding, food inhalation (eating food like a vaccum) or some other thing that got mentioned earlier are not so simple to fix or work around.
When gypsy was being trained by a professional trainer, he suggested using chicken for the training treats. And that worked extremely well.
