Hello, I have a 16 week old puppy and I live in a flat which has one flight of stairs to get up to. When we first starting taking him outside he wouldn't go downstairs, which I know is common. However, he didn't have a problem running back up. The last week, he was been refusing to walk back up the stairs. I have no idea what has changed. I have tried tempting him with treats, even putting treats on each step. I have tried getting excited and running up the stairs to see if he follows and I've also tried putting him on one step at a time. All with no joy, he is so stubborn and just sits there! I am all out of ideas... Can anyone help?