Thanks for your enquiry.
The fact that your former Solicitor does not appear still to be in business, will not hinder you getting the decree absolute (which is the document proving that you are divorced).
However, as it is more than 12 months after the decree nisi, when you apply for the decree absolute, you will have to give an explanation in writing with the application containing the following information:
a) why the application was not made earlier
b) a statement as to whether the parties have lived together (including any dates) since the decree nisi/conditional order
c) a statement as to whether any child has been born to a female petitioner and/or respondent and, if so if the child is to be considered a child of the family.
You are free to go and see another Solicitor to assist you with your application.
If you wish to provide me with the firm of Solicitors who acted for your previously, I can do a search for you to see if they are still trading, but as I have said, you don't have to go back to them.
I hope this answers your question, but please let me know if I can assist further.