Hello, my name isXXXXX and I have over 20 years of experience as a veterinarian.
I'm sorry to hear that Max doesn't want to use his new dog house.
I know it seems strange to you but in his eyes it is perfectly understandable. In all likelihood he had no idea that this is "his" house. Imagine if you came home from work one day and your house was torn down and a beautiful new home was in its place, much nicer then your home. You would be upset and puzzled and wouldn't just start using the new home. He is being polite and probably waiting to see who moves in. It may even smell like another dog or another creature, depending upon where it was stored before you bought it.
We need to teach him that the new home is his, and safe to live in.
If you have pieces of his old home you may want to put them on and in the new place so it looks and smells like his old home.
Rub blankets on him to get his scent on them, then place them inside the new home.
Place his favorite toys in the new place too.
Continue feeding him in his new home and praise him profusely when he goes in the new house.
It may help to hide treats in the blankets in the new house so he has something to do in there that occupies his mind and gets him used to spending time in there.
You may also want to spray the inside of the new dog house with a product called DAP (dog appeasing pheromone) which is a synthetic analog of a pheromone that a nursing bitch produces that many dogs find soothing.
This may take time, as Max sounds like a very polite fellow, but hopefully with patience and training we can get him comfortable and he will officially move in.