Hello,
Mr. McGibney has hit the nail on the head, with regards to what is actually causing the problem.
A quick call, or visit to the accountant's offices, should get you an answer to the initial question.
If it's a case of the accountant just going AWOL, I would first send him/her a registered letter, politely setting out the problem, concerns and need for (immediate) remedy. Give them a reasonable amount of time to respond.
Assuming no satisfaction from the above, I would next contact whichever professional body the accountant is a member of. Most will try and assist you, and also have disciplinary options available to them, if needed.
Assuming you still don't get any joy, the Accountant will also have Professional Indemnity cover, if you can show a loss as a result of their actions (or lack of action). Obviously, that's one for our solicitor and the last port of call.