…...A Sin that Will Not Be Forgiven...

"And another angel, a third, followed them, saying with a loud voice,
"If any one worships the beast and its image, and receives a mark on his forehead or on his hand, he also shall drink the wine of God's wrath, poured unmixed into the cup of his anger, and he shall be tormented with fire and sulphur in the presence of the holy angels and in the presence of the Lamb. And the smoke of their torment goes up for ever and ever; and they have no rest, day or night, these worshipers of the beast and its image, and whoever receives the mark of its name." (Rv 14:9-11)

As we see from the citation above, anyone who willingly accepts the subdermal microchip placed in their body will go to Hell irrevocably upon his death.
Willful acceptance of the markof the Beast constitutes a sin that will NOT be forgiven. That is because by doing so, one loses his free will and ability to seek forgiveness.