Dog Won't Poop on Training Pad?

I have a 2 month old Maltese Terrier and it is too young to go out of the house. Currently she has a training pad where she only does pee.

When we realise that she is going to poop, we put her on the training pad and keep her there for one hour, but she still doesn't poop. As soon as we are convinced that she isn't going to poop she goes and does her business on the floor. What do I do to get her to poop on the training pad?

By massimac