Bring a motion compelling them to do so?
Mind you, the question you ask begs even more questions...........
Is the solicitor not responding because
1. They have no instructions? From their own client
2. They are the Plaintiff/Defendant and don't feel like it?
And are you a lay litigant? or do you have a solicitor you could direct the question to? They would have a far better idea of what is going on and you would get a great deal more info and better answer than posting very broad questions on this board.
mf