I wasn't fully aware you could continue to advise them after they declined.Invite them repeatedly. Eventually they'll want to play a game with you to decide. If you lose, keep asking them until they ask to play the game again.
I recently got/am getting Cousteau from the campsite. It took probably 30 minutes of talking to him to finally convince him to move in, partly because I lost the game once.
It took a few resets before I could get the camper to move in.
Thanks~