Well, if your ex-souse is no longer paying child support, one of the mechanism that you can use is that you can file a motion for contempt and reopen the court case. He or she will be brought before a judge to see why he or she is no paying the child support obligation. If a judge finds that their lack of paying child support was willful, the judge can hold the party in contempt at that time. If they are making a  good faith effort to pay at least some of their child support obligation, that will certainly be taken into consideration.