How can I deal with a professor who refuses to communicate?
Given the reluctance of anyone else to communicate with Prof A, it seems less a case of you not knowing the secret handshake to get in touch with him, but more a case of Prof A simply not communicating. It is unlikely that anyone (including the dean) can make him communicate in a reasonable way.
What you need to do is to make sure that the path-of-least-resistance for your department is something that ends with you graduating very soon. My guess is that the best bet for that would be to get someone else to examine you. The &quot;Vorsitzende(r) des Pruefungsausschuss&quot; should be able to authorize such a thing. Phrase it as &quot;Prof A is unavailable for examinations&quot;, not as &quot;I failed to get in touch with him&quot;. If they claim that Prof A is available, ask them to demonstrate by telling you the date for the exam. Be polite but persistent.