My ex won’t sign the iD1 but has been bought out.

Chezza3012

I split up from my ex and at the time the mortgage was in his sole name even though I contributed half to all bills and expenses. We have a child but separated over 3 years ago. I stayed in the family home and Paid the mortgage and all bills from the day he left and received no monies from him by way of maintainability for our child. It was eventually agreed that I would buy him out and employed a solicitor to ensure this was done correctly. 

He received over 25k, I have now been informed by the solicitor 2 years on that he had not signed the ID1 form despite being contacted numerous times and that I may have to take him to court to get his name off the deeds. 

Does this mean he still owns half the house and are the solicitors responsible for this situation. My ex is extremely vindictive and I am so worried. 

I would really appreciate any advice.