New Living Translation
Yes, they knew God, but they wouldn’t worship him as God or even give him thanks. And they began to think up foolish ideas of what God was like. As a result, their minds became dark and confused.

American Standard Version
because that, knowing God, they glorified him not as God, neither gave thanks; but became vain in their reasonings, and their senseless heart was darkened.

Berean Study Bible
For although they knew God, they neither glorified Him as God nor gave thanks to Him, but they became futile in their thinking and darkened in their foolish hearts.

Douay-Rheims Bible
Because that, when they knew God, they have not glorified him as God, or given thanks; but became vain in their thoughts, and their foolish heart was darkened.

English Revised Version
because that, knowing God, they glorified him not as God, neither gave thanks; but became vain in their reasonings, and their senseless heart was darkened.

King James Bible
Because that, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened.

World English Bible
Because, knowing God, they didn't glorify him as God, neither gave thanks, but became vain in their reasoning, and their senseless heart was darkened.

Young's Literal Translation
because, having known God they did not glorify Him as God, nor gave thanks, but were made vain in their reasonings, and their unintelligent heart was darkened,

Romans 1:21 Additional Translations ...