The atheist says there is no God. Ask them "If all the knowledge mankind has ever known was depicted by the interior of a circle, what portion of that circle could they shade in to represent what they themselves know for sure." Most people would say they could only make a tiny dot within that circle. Then tell them "Let's overestimate what you know, and shade in half of the circle, to represent that you know half of all that mankind has ever known. Wouldn't it be "possible" that in the other half of the circle could be knowledge that God really does exist?" An honest person would have to say "Yes, that would be possible." Therefore, no longer being able to "honestly" say they "KNOW" there is no God, if they were honest, they would have to say they are not truly an atheist, but an agnostic that says they don't know absolutely for sure whether there is a God or not.
Sorry, but most atheists are learning to willingly conflate atheism with agnosticism, and declare that it is, in fact, what they do not know, or what they have been presented with no conclusive proof for, that makes them persist in their unbelief. The most cleverly-crafted, logical discourse will never, of itself, dissuade the convinced atheist from the belief that there is no God. Even when we have succeeded in efforts to engage productively with skeptics, sufficient credit and glory to God, His Word, and His Spirit are seldom, if ever, offered. This is why so little of the progress we crave eludes us. God is waiting for us to allow and bid Him do the work. May he have mercy on our prideful souls.