Puppy

We recently got our sweetest puppy, who’s a basset hound. We are struggling to get him to eat, it’s weird to say but he acts like a picky eater. The previous owner explained that she had him on goat milk, we bought some and he does drink that. However, he refuses to eat any kibble, any soft food, any treats. The one thing he eats is salami which I discovered accidentally. All other foods he seems uninterested in. What’s concerning is he’s got his ribs poking out now. He’s not lethargic or anything and loves to play, I’m just worried why my puppy can’t eat. What’s the solution?