I can find no place in Revelation where John states that the “Church” is in heaven where he is during the tribulation. The ones in Heaven are God, Jesus, the Elders, the angels and those Christians under the seat of God that have been killed for their belief in God and Jesus. The only others that show up in Heaven are the slain that come out of the great tribulation. So where is the “Church”?
Rev. 5:8-10 (KJV) says,
And when he had taken the book, the four beasts and four and twenty elders fell down before the Lamb, having every one of them harps, and golden vials full of odours, which are the prayers of saints. And they sung a new song, saying, Thou art worthy to take the book, and to open the seals thereof: for thou wast slain, and hast redeemed us to God by thy blood out of every kindred, and tongue, and people, and nation; And hast made us unto our God kings and priests: and we shall reign on the earth.
The four beasts (Cherubim) could not sing this song alone. They’ve been the guardians of God’s throne since before time began, and are part of the angelic realm. The only way the 24 elders could sing it is if they represent the Church. Only the church has been redeemed by the blood of Jesus out of every kindred, and tongue, and people, and nation and only the church will be made Kings and Priests to reign on Earth.
These elders are never shown in Old Testament visions of the Throne of God, but in Rev. 4 they’re shown seated on thrones like kings, they’re dressed in white which means they’re righteous, and they’re wearing the crowns of over comers. Only the Church fits that description.
The martyrs of Rev. 6 are under the altar, not seated on thrones. And the multitude in Rev. 7 serve God in His Temple but don’t reign with Him and are never called either kings or priests.