Unrealistic expectations are a frequent cause of problems in housetraining.
On average, the bladder/brain connection is not fully formed until the puppy is about 8 months old. If a young puppy does go to the door and “ask to go out,” his need is immediate, he must go out right away. Some dogs never learn to ask to go out, while others learn quickly to go to the door and sit or bark or ring a bell. Some dogs learn to use a dog door easily and go out whenever they feel the urge.
The best way to ensure success is to stick to a schedule long enough for the puppy’s body to adapt to it and get in the habit of eliminating at particular times.