You can go to court with either an OSC or a Motion to enforce the Judgment. You simply tell the judge that your ex has not complied with the judgment and ask for an order compelling him to do what he is supposed to do. Of course, this will only work if he can do it. If your ex really cannot get the loan, you may have to simply sell the house.
Best of luck to you.
This response is intended to be a general statement of law, should not be relied upon as legal advice and does not create an attorney/client relationship.
You need a motion to enforce, or motion to compel. You should employ a local attorney to protect your rights.
This answer is offered for informational purposes only. It is not offered as, and does not constitute, legal advice. Laws vary widely from state to state. You should rely only on the advice given to you during a personal consultation by a local attorney who is thoroughly familiar with state laws and the area of practice in which your concern lies.