Potty training advice

I recently got a 15 week old Cavapoo and have not had much luck with the potty training aspect. I’ve only had him for just about a week but am struggling in the potty training aspect. I know you’re supposed to reinforce good behavior (I’ve potty trained a few dogs) but this puppy just will not go to the bathroom outside. I’m not sure if it’s too cold (I live in Michigan and it has been 30-40 degrees). We talk him out on an interval schedule every thirty minutes. He will walk around for twenty minutes or so but will wait until he gets inside to use the bathroom. When he uses the bathroom inside we tell him no and immediately take him outside to signify the correct place to use the restroom. Nothing is working. Is there something else I should be doing? I want to correct this behavior before it forms too much of a bad habit.