My child's father is not making child support payments. What can I do to enforce it?

You do what fathers can't do trying to enforce their parental rights, you get free government help their a fully funded government agency that will chase him to the ends of the Earth, and the end of time, to make his pay, even when he doesn't owe anything. At least the vast majority of fathers pay, compared to only 5% of mothers.

If the court ordered him to pay child support and he's not doing it, tell the court what's going on. Child Support Enforcement will take him to court and force him to liquidate assets, garnish his wages or send him to jail.

Contact the child support enforcement agency in your area. You don't need to shell out the money for an attorney if your kid's dad was ordered to pay support. That's their job to enforce a court order. You may not see any money any time soon, but they can make life rough for him at the very least. +4
Real men take care of their children, choose wisely next time :)

go to your social services office. child support enforcment is a free government service.
here is a more noble idea. offer to release him of his paternal responsibility if he will release his paternal rights. that is what I am offering my soon to be ex wife and we even had planned to raise jacob together. she is taking the offer.

Get a lawyer of course.