What to do if my divorce decree states that my ex and I split the cost of the children's extracurricular activities within 15 days of the request, however he is refusing to pay?
Your recourse is to pursue contempt of court against your ex.
You will need to file with the court an Order to Show Cause for a hearing on your contempt of court claim. Call the court clerk to schedule a hearing. Include the date/time/department of the hearing on your Order to Show Cause. Also file a declaration signed under penalty of perjury stating the facts in support of your contempt of court claim. File any other supporting evidence. File a proof of service (court form). Mail a copy of your court-filed documents to your ex to give your ex notice of the hearing. The proof of service verifies the date of mailing.
Prior to filing your documents with the court, ask the court clerk if any other documents are required to be filed for contempt of court because the required documents may vary from state to state.