What does Isaiah 22:14 mean?

Then the Lord of all spoke to me and said, 'This guilt won’t be forgiven as long as you live.' That’s what the Lord, the Eternal One, has declared. Isaiah 22:14 - Modern Text Bible

(God tells Isaiah that the people’s sin is so serious that there’s no way it will be overlooked or wiped away during their lifetimes. This is a final, sobering warning.)