I am sorry to hear about this concern.
Ensure he is breathing okay and the nostrils are clear.
You could try giving a little pancake syrup (1/4 teaspoon) to try and stimulate before using the milk.
Make sure you have an appropriate nipple for nursing.
Here some other info:
However! for this safety of this puppy, I must strongly encourage you go into an ER clinic for supportive care, as improper feeding could result in quick deterioration of this puppy, and we don't know if there are any other health issues exacerbating the problem.