Why didn't David ascend into heaven?
Acts 2:34 says that David did not ascend into heaven. Why? Acts chapter 2 describes David's prophecy about a bodily resurrection. Peter makes it clear that David's prophecy could not refer to David's bodily resurrection since David in fact died and experienced corruption and his grave could be seen as evidence or this corruption. As David did not bodily rise from the dead, he did not ascend into heaven either. The contrast is between the dead, corrupted body of David in his tomb and the living Christ raised immortal. David's body underwent corruption; Christ's body did not, but was raised immortal and incorruptible. Christ is clearly superior to David and He is David's Lord.
The real question that the Jehovah's Witness needs to answer is where will David be in the resurrection? The Watchtower teaches that the Old Testament Prophets will be resurrected to live on the earth as they are not part of the 144,000 select group of Jehovah's Witnesses to go to Heaven. In contrast, the Bible teaches that Abraham, Isaac and Jacob will be in Heaven. Jesus said, "And I say to you that many will come from east and west and sit down with Abraham, Isaac, and Jacob in the Kingdom of heaven." Matthew 8:11.
Jesus certainly did not exclude the Old Testament saints from the Kingdom of Heaven. Job looked forward to the time that he would be in the Kingdom of God and would actually see God for himself, "For I know that my Redeemer lives, and He shall stand at last on the earth; and after my skin is destroyed, this I know, that in my flesh, I shall see God, whom I shall see for myself, and my eyes shall behold, and not another." Job 19:25-27.
Job believed that a time was coming that men would be able to see God and he believed that he himself would see God with his own eyes. Revelation 21 repeats this hope with a promise, "And I saw a new heaven and a new earth, for the first heaven and the first earth had passed away. Also there was no more sea. Then I, John saw the holy city, New Jerusalem, coming down out of heaven, from God, prepared as a bride adorned for her husband. And I heard a loud voice from heaven saying, Behold, the tabernacle of God is with men, and He will dwell with them, and they shall be His people, and God Himself will be with them and be their God....They shall see His face, and His name shall be on their foreheads.'" Revelation 21:3 & 22:4.
Fellowship with God restored
The fellowship with God that Adam lost in the garden is finally restored for mankind in the book of Revelation. In contrast to the Watchtower's doctrine of two separate kingdoms -the kingdom of earth and the kingdom of heaven, the Bible speaks of one Kingdom where the new Jerusalem (the city of God) is brought down to earth and the kings of the earth may enter the city. "And the nations of those who are saved shall walk in its light, and the kings of the earth bring their glory and honor into it." Revelation 21:24. How can one enter this Kingdom? Jesus said that there was only one way, "Most assuredly, I say to you, unless one is born again, he cannot see the kingdom of God." John 3:3. Jesus condemned the religious leaders of his day when they shut up the kingdom of heaven to the common people, "But woe to you, scribes and Pharisees, hypocrites! For you shut up the kingdom of heaven against men; for you neither go in yourselves, nor do you allow those who are entering to go in." Matthew 23:13.