I addressed this question in an earlier series of posts. The allegation of silence began in 1963 with a play, The Deputy by Rolf Hochhuth. The 1999 book Hitler's Pope popularized the idea. Largely, the debate over Pius XII's actions during the war has been taken up by partisans. Some authors have demonstrated an axe to grind against the papacy or Catholicism and have let that bias affect their work. Other authors have demonstrated a bias in favor of the papacy or Catholicism and have let that affect their work as well. This has sadly left little room for real historical inquiry. In summary, the papacy was not silent during the Holocaust, but its words were couched in diplomatic language and the Vatican was bound by treaty to observe strict neutrality in foreign affairs.

As always, followup questions by OP or others are encouraged.