New puppy absolutely refuses to potty outside.

I just have a pit/aussie mix that's 8 weeks old, and I've had him for 2 days now, and in those 2 days, he absolutely refuses to pee or poo outside. I have a grass pad on my apartment balcony until he gets his shots, and I take him there when he wakes up, after drinking water, after eating, every hour/ 30 mins, etc., and will stand there for 15-20 minutes, and all he will do is sit and whine, but the second he's back inside, he pees in seconds. It's winter, so maybe the cold has something to do with it, since he just whines and shivers when he's outside. The family I got him from said he was using puppy pads, so maybe that has something to do with it. Just seeking advice on what to do, and hoping maybe just giving him time to adjust will work, but I feel as if I'm doing something wrong.