Curious has any one ever had a pup (now 9 mths old)that would not go up or down inside house stairs, bounds up & down deck stairs & stairs to back yard, but will not do a flight of house stairs. I've tried coazing with treats, nope that doesn't work, I tried putting her half way up the stairs then tried calling her, nope just stood there wouldn't move a inch. I don't have a clue why she's afraid never had a bad experience with stairs.

Carpeted or bare wood? Open risers?

I had a girl that was terrified of stairs and slippery floors. Her mother was the same or worse. Lots of patience made her at least come into the rooms, but very hesitant. She never mastered the stairs. I had to force here to go up, and she would go down by herself. Close stairs where she couldn't see through, were less frightening.
You may try some anxiety medications. Ask your vet.

Take one step at a time. Guide or place pup on lower step, kneel down on floor with a treat, guide pup down to get the treat, make a big fuss. Then put pup on floor guide pup up step with treat. Then do two steps, then three and so on. You will be surprised at how fast they catch on.

Are the house stairs longer? It might just feel too overwhelming for him. If you have another dog that is good with stairs, put the pup on the leash and go up with the other dog. I use the leash to keep the pup's head up (especially on open stairs) and focused on the top. If not, then get some special treats only for this exercise, and start day 1 with the treats on the first step. Second day the second step, third day the third step and so on. Praise when he takes the treat. The first couple should be easily in reach, then the pup will have to put a foot or two on the steps to get the treat. When the pup can't reach and seems "stuck" at the bottom, just stay at the top of the stairs and wait. It might take a while but never give the special treat unless he takes it off the step. You could also do this with breakfast or dinner if he's a really good eater. I would put breakfast away if he doesn't get to the right step and try again at dinner time when he's hungrier. You could use a leash and collar for some gentle encouragement. Always walk confidently up the stairs yourself as if you expect the pup to come with you without a problem. If you hesitate, it reinforces that there might be something to be afraid of. Good luck!!!

Know a certain line from one stud who did this, produced puppies that did the same thing for two generations that I followed-really was something. One boy lived with me and he was not my first lab and lived with 2 other labs. Would do outside stairs of 3-5, would do some inside stairs IF the stairway was open-never would do basement stairs no matter how much training we did, and we did it! Also would not follow the other dogs up or down. Needless to say I was surprised when meeting up with the original studs owner at a show and mentioning this to hear he did the same thing...