Well, it is a broad question. Here is the thing. It is possible that there is an issue with the food itself, such as a) it might have rancid fats, b) it might contain something that doesn’t agree with your pup’s system … more importantly, your pup might not be feeling well. Here is how that works – some foods are more attractive/palatable than others and entice being eaten even if the stomach feels upset. For example, we had a similar problem with Jasmine (also since she was a pup) and eventually it turned out she had IBD.
I’d starting by having a close look at the food, followed by a vet evaluation. This might not be an easy thing to figure out but it is important that you do.
Your infant puppy should be feeding off its mother right now. Is there a reason this isn’t a possibility?
the best feeding for an infant puppy (or any animal for that matter) is from its mother. If that isn’t a possibility, then I would contact my vet- you’ll find that between routine vaccinations and check ups that you will be at the vets office quite a bit over the next year with your new friend? Your veterinarian will be able to guide you through everything you will need to know and more. Very best of luck!