In the New American Bible - Revised Edition (hereafter, "NABRE"), the primary translation used among English-speaking American Catholics, Isaiah 8:19-20 reads this way: "When they say to you, 'Inquire of ghosts and soothsayers who chirp and mutter; should not a people inquire of their gods, consulting the dead on behalf of the living, for instruction and testimony?' Surely, those who speak like this this are the ones for whom there is no dawn." Notice the phrase that I have placed in italics. The translators of this version place it in the assertions of those who seek advice from mediums.
In contrast, the ESV reads, "When they say to you, 'Inquire of the mediums and the necromancers who
chirp and mutter,' should not a people inquire of their God? Should they
inquire of the dead on behalf of the living? To the teaching and to the testimony! If they will not speak according to this word, it is because they have no dawn." Here, the translators place the clause in the portion in which God rebukes this paganistic syncretism. It is placed the same way in the New King James Version and the Modern English Version, which follow a different manuscript tradition. It was even placed this way in the Douay-Rheims Version, a much-earlier Catholic bible, in even stranger phrasing: "To the law rather, and to the testimony."
One of the five solas of the Reformation was "sola scriptura," or "scripture alone," the belief that the Bible alone is infallible, and is therefore the ultimate standard for judging any question of spiritual controversy. Protestants believe that God has placed all truth necessary to salvation and godly living in the Bible, so that any man or woman can read it for himself, without the need of a priest or pope to give him "the rest of the story." This doctrine freed the conscience of Christians from the bondage that they had known to the hierarchy of the Catholic Church. Thus, that hierarchy, the force behind the translation of the NABRE, had a vested interest in hiding the truth revealed in these verses, the truth of sola scriptura!
Catholic apologists love to challenge Protestants with the question, "But where does the Bible teach sola scriptura?" And, since most Protestants don't know their bibles, especially the Old Testament, they often do not know these verses. And the Catholic hierarchy works hard that their own people do not know them, either.