Enforcement of separation agreement

Good morning: My BF has been divorced from his wife for almost 5 years. All issues have been settled, and the original separation agreement included property division. His ex got the house. However, he is still on the mortgage and the deed, and has been trying to get off of it for 5 years. They have an assumable mortgage. At the end of April, they entered into a modification of the separation agreement, whereby he was to sign over the deed to her, and she was to either assume the current mortgage, or refinance to remove him from the current mortgage within 30 days of his signing of the deed. It has now been 30 days, and it appears as if she is not going to qualify for either a refinance or the assumption. Unfortunately, the new agreement is silent on what happens in the event she doesnt refi or assume. What can he do now to get himself off the current mortgage? What if she’s already filed the deed that he signed over to her?