If she is required to sign a listing agreement as part of the divorce judgment, then you can file a motion to enforce the order. Otherwise, you can file a petition requesting the court to order the sale. I would recommend consulting with an experienced family law attorney to discuss your options in detail.
Your question does not indicate whether you have a separation agreement or the sale of the house was part of the Court Order after a trial. If you have an agreement you can consider filing for a Contempt to enforce. If it is only by Court Order you may file for partition and sale of the home and other relief. You can ask the Court to grant you financial relief by crediting you for payments made on the mortgage. Sit down with a lawyer for a more detailed analysis and options.
Sign up to receive a 10-part series of useful information and legal advice about the divorce process.