Do you discipline him when you catch him in the act? I say a stern "no!" And then I carry my boy straight to the pad and tell him "pee". It's tough at first but helpful if they associate the word "pee" when they're on the pad bc eventually you can demand that they pee when you place them there. It's quite amazing
actually. So after mine learnt the word, if he was caught marking somewhere, I carry him to the pad and repeat over and over for him to pee and eventually (sometimes 15 mins later in the beginning) he does it where he's supposed to and I praise him and give him a treat. until that happens I would take him to the pad more frequently. He will catch on quickly, it seems he just needs some reinforcement. Are you able to keep him in a small area when you aren't home? Or maybe in a playpen? This may help a lot too until he is fully house trained. Good luck! They are very smart and bad habits are easier to break at a young age. Just be diligent.