1 John 3:9 ("whoever is born of God does not sin") doesn't mean Christians never sin. 1 John 1:8-10 in the SAME letter says "if we say we have no sin, we deceive ourselves" and "if we confess our sins, he is faithful to forgive." The Greek tense in 3:9 indicates ongoing habitual practice, not individual acts. A Christian won't be characterized by a lifestyle of sin, but will still fail and need forgiveness.

1 John 1:8: "If we say we have no sin, we deceive ourselves." 1 John 1:10: "If we say we have not sinned, we make him a liar." 1 John 2:1: "If anyone sins, we have an advocate with the Father." Same author, same letter, clearly expects Christians to sin sometimes. The resolution: 1 John 3:9 uses a Greek construction indicating habitual ongoing practice — a Christian doesn't practice sin as a lifestyle, but individual failures are expected.