It could be that your puppy doesn't like getting on the leash.
I had a puppy that would not go for a walk if I got out the leash and he would go hide under the couch but if I didn't have the leash in hand he would gladly go outside with me and walk.
Sometimes I would have to pick him up without the leash in my hand and then once outside grab the leash off the porch and put it on him.
Sometimes he still refused to walk but eventually got used to it once he figured I wasn't walking him without his leash on.
So it may just take time to get the puppy used to it's leash or the puppy could just be tired and not want to go for a walk.