I have a 5 1/2 year old yellow lab. We live in a 2 story house. Our lab is very active and gets good exercise though he is a bit overweight. We got him when he was just a few weeks old. We dealt with the trials of raising an extremely intelligent and curious dog. When he was a puppy, he was afraid up the stairs and he had to be carried up but never had a problem going down the stairs or going both up and down the outside stairs. .
Ever since he reached adult hood, sometimes, he refuses to go up the stairs inside the house. He will sit at the bottom of the stairs and bark and whimper. It does not happen often though. BUt when he does, I just open the door and he runs outside and runs up the outside stairs to the upstairs entrance. The inside stairs are wood and the outside ones are concrete with ceramic tile.
the only thing that comes to mind is, my wife and I had to dash off for an emergency appointment yesterday and I did not pet him and tell him good bye and tell him to take care of the house and be a good boy so he reverted to puppy like behavior to get the attention he received when was tiny. I am in my 60's and have several dogs in my life but this is my first lab. He certainly has some behavior traits I have never seen in a dog before. He can be very silly. When we have left him alone before, a couple times, if the bedroom doors are not closed, he pulls all the pillows off the beds and strews them around the house. He does other things, to numerous to mention, that make me laugh and he sits there, wagging his tail and smiling.