Welcome Nan!
The NWT reads:
9
And they sing a new song, saying: "You are worthy to take the scroll and open its seals, because you were slaughtered and with your blood you bought persons for God out of every tribe and tongue and people and nation,
10 and you made them to be a kingdom and priests to our God, and they are to rule as kings
over the earth."
A conversation with a Christadelphian some time ago brought me to this Watchtower explanation:
In support of their position that no one of earth will ever go to heaven and that God?s kingdom will be wholly an earthly one Christadelphian writers cite such texts as: "The Lord of hosts shall reign in mount Zion, and in Jerusalem." "The Lord shall be king over all the earth." "And hast made us unto our God kings and priests: and we shall reign on the earth."?Isa. 24:23; Zech. 14:9; Rev. 5:10
the third text, telling of Christians reigning "on" the earth, the Greek word here translated "on" is epi, and it can just as well be rendered "over" as "on," and in fact is rendered "over" by such Bible translators as Goodspeed, Knox, Weymouth and the New World Bible Translation Committee.
Knox, born a protestant, converted to Roman Catholicism and translated the Vulgate (ie not Greek manuscripts) from the Latin to English. Knox's 'over' is a translation of 'super' in the Latin Vulgate. It is not, technically, as claimed by the WTBTS, a direct translation of 'epi' from Greek because Knox's aim was to produce an English translation of the Latin Vulgate. His efforts were overshadowed by the "Divino Afflante Spiritu" 1943, promoting Biblical studies and use of original language sources.
Weymouth, is at variance with the NWT with:
John 1: 1 - 3In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God.
Goodspeed, at variance for his use of L ORD in place of the Tetragrammaton .
Is this of help?