If you had your puppy checked out and the vet says everything is fine. And if your puppy WILL eat treats, just not interested in regular food.... then is sounds like you have a picky eater on your hands.
I had one too! My GSD Elsa Rose was a picky eater for most of her life. Initially everyone said 'Don't let her be the boss'....'Hang tough and take up the food she won't starve to death'...... 'This is a control issue and you can't give in'.....
So I picked up the food everytime she wandered off from the bowl for over 3 days and watched my already skinny girl dog lose weight (over 5 pounds) and she could care less. Still would enjoy eating her training treats though!
I decided that the recommendations I had been given were ridiculous for my situation. It appeared that regular dog food just was boring and uninteresting for Elsa, so she'd pass. Rather than me continuing to hang tough to 'show her' and prove something (not sure what at this point except that she could indeed still walk around and appear healthy with all her ribs hanging out), I decided to come up with a solution that would get her eating.
It appeared that any regular kibble, ANY type, would quickly become boring to her so she'd start skipping the meals. It also appeared that adding something yummy to the 'boring' kibble would get her to not only start eating but FINISH eating.
My goal became to figure out the least amount of an additive to add to her normal kibble amount to get her to eat. Fairly quickly I determined that any of my leftovers in the fridge would work. A surprisingly small amount (1/4 cup or less) of cut up teeny pizza/chicken/spagetti/beef/cottage cheese/yogurt/mashed potatoes/buttered green beans....... almost ANY human food....... MIXED WITH WATER to make a gravy to coat the kibble with the flavor would have my dog eat her meals.
Another really easy go-to for me was found in the cat food aisle. I would buy a bunch of cans of CAT food that were on sale, different flavors and brands cause variety seemed to be a key element to keep my dog eating.
This sized can. The amazing thing about cat food is the companies know cats are finicky so they have to make the food super stinky and yummy. Well those same stinky/yummy factors worked for my dog. Plus ONLY 1/4 or 1/3 of this can, MIXED WITH WATER, and added to the kibble pretty much guaranteed the meal would be licked up to the last drop.
So easy to store the rest of the can in the fridge with the plastic pet lids you can purchase. And easy to travel with and store if you are away from home!