I have the same problem with Paddington!!!! I walk him for about an hour every evening, and he NEVER goes! He'll come inside and go on the floor. During training class, we'll take our dogs out to potty, and he won't go while we are outside in the potty area- but he will go right in the middle of the training pen, when all the other doggies and mommies are watching
I mean we JUST went out! He pees and poops outside at home, but nowhere else outside. He just sniffs where other dogs have peed. I think my problem is that I have trained him to go on a pad as well as outside. I think it confused him, but I had no choice but to do it this way.
I wish I had a solution, but I just wanted to share empathy with you! I hope someone has solved this problem in the past
-O