If your dog was trained to potty indoors on training pads, it might be challenging Some dogs may be saving some pee or poop to mark it.
Do not praise your puppy for using the pad, but never scold her, either. Save the praise for those hard-earned outside pees and poops.
Our dog was pee-pad trained when we adopted her at 6mo. We did not use pee pads to try to break her of this habit right off the bat and took her outside.