When man sinned and did not repent he lost his spiritual dynamic of direct communication with God and now the consequence of this is that all the descendents are spiritually inert or dead without spiritual inspiration. The veil of sin had been put between us and God. Adam had died in the spirit reducing him to a defiled triune in makeup, body and soul. “But” this does not mean that man has no conscience, but that his conscience is not impacted by the Holy Spirit as it is in the believer. By way of example; we could take some elements like a clear glass of water at room temperature and we can see though it, but if we drop another element in like some ink into the water it becomes cloudy and less transparent. The sin in man is like the ink clouding his thinking.
The diagram below shows the difference of the original design to the fallen state of man.
We are the descendents of Adam born into this world with a spirit that is dead. Our conscience is seared to the things of God and we operate in our makeup being governed by our mind and body. But once we become aware of the knowledge of good and evil, then the penalties of sin fall upon us. Following this we receive, by the leading of the Spirit of God, the realization for the need to repent of our own sins. Then to accept that Jesus is the required atonement for our sins we can be saved.
Once we have taken the step of repentance salvation is given to us and the cleansing work begins by the grace of God.