Tinder, at least the free version, has become a poor app for meeting people. The app puts the unpaid users to the bottom of the pile under all the paid users. Only those going through all the paid profiles will get down to the free ones.
Your son really needs better pictures. Find someone with photography skills and photo editing skills to raise his perceived attractiveness and thus his ELO score. Good pictures get selected way more often than poor ones, and getting selected keeps the profile toward the top of the pile.
He should add Hinge, Bumble, Coffee meets Bagel, and other free apps. Especially in thinly populated areas he needs to play the numbers game.