The prophetic sealing includes both blessings and cursings (the “wo unto them” statements). The cursings are an important part of sealing. The plates become a blessing or a curse, depending upon how we approach them and the witness that we receive through faith.
Those who deny the gifts of God are those who not only lack faith but who have also rejected Christ. As a result, when they die, “they die in their sins,” Christ’s atonement for sin will not take effect on their behalf, and they will suffer spiritual death. They therefore remain as though there had been no atonement.