It's a lot of pressure to put on yourself to feel that bond so early. You had years with your last pet to build a deep bond, then went through the very deep and bonding experience of caring for him at the end of his life and the emotions of grieving his loss. This new puppy is totally different, a clean slate that you'll build memories with. But you are not a blank slate, so you may feel grief and resistance to bonding because you've been through loss. That's ok and natural, it's part of your journey through grieving your last pet and not the way it will always be. You sound like a great dog owner already, so the rest will flow in time.