If the court has ordered that a parent must pay child support, it is a criminal offence not to pay.
Go to the maintenance office and complain. It is important to make a formal complaint every time when the other parent doesn't pay.
The maintenance office records each time the other parent pays. This record will show when they do not pay and how much they owe.
If the other parent is employed and failed to pay maintenance, you must ask the court to make an order to get the maintenance directly from their employer.
If the other party does not pay, they are not obeying the order of court. This is a crime. The court will send them a notice telling them to come to court on a certain date. They must then explain why they did not pay the money. If there isn't a good reason, the court will usually tell the other party that they must pay all the maintenance they owe, or they will go to jail.