I taught my 1st puppy Tyson within 2 days. My new puppy Odin learnt around the same time. Only time they potty outside the pads is when the pads were already pee'd/poo'd on, but to avoid that just keep clean fresh pads on the spot you've selected.
What I do is, whenever Tyson or Odin pee'd or poo'd, I'd grab the puppy and bring it close to the scene of crime and give him a "no!" with a slight heavy voice, then with some absorbent tissue I'd wipe it and let him smell the tissue, then carry him to the pads and wipe the pee or poo on the pad and let him smell it. After 2 or 3 times, he gets the message.
I had a particularly bad time with Tyson cos he arrived at my home pretty sick, with a month long Kennel Cough so it was impossible to take him outside, so I found this technique very effective and helped keep my house clean. Tyson would even go vomit on the pads, that's how well this worked cos he realized anything coming out of his body had to go on the pads (and he's very smart too). And he'd vomit at least once or twice a day due to the severe Kennel Cough.
Hopes this helps in case you haven't had success yet!