There is a lot of confusion about the Kingdom of God and what it is and when it will come. But did it already come and we just haven't noticed it? Will it come in the future?
Well, Jesus was very clear when He said that "The Kingdom of God does not come in ways observable" and "The Kingdom of God is within you"
So it's clear that it was not or is not coming in ways that can be physically observed. If you believe that there will be a future physical Kingdom coming, with all due respect, you are incorrect. This can be refuted heartily with plenty of scripture but just one for now was when Jesus made His emphatic declaration about the nature of the Kingdom of God...
"Being asked by the Pharisees when the kingdom of God would come, he answered them, “The kingdom of God is NOT coming in ways that can be observed." Luke 17:20
But what about the "when"? When would the Kingdom actually come? Well, around 33ad or so, Jesus made the following statements...
"Truly, I say to you, there are some standing here who will not taste death until they see the Son of Man COMING IN HIS KINGDOM" Matthew 16:28
"When they persecute you in one town, flee to the next, for truly, I say to you, you will not have gone through all the towns of Israel before the Son of Man COMES." Matthew 10:23
"Therefore you also must be ready, for the Son of Man is coming at an hour you do not expect...Truly, I say to you, THIS generation will not pass away until all these things take place." Matthew 24
So we have Christ assuring THEM that He would return before they would die, before they would finish preaching in ISRAEL, and before that generation would pass away. So let's compare that to the Lord's prayer and see what we can find out...
When Jesus told His disciples to pray, He told them to pray like this...
"Our Father in heaven, hallowed be your name. YOUR KINGDOM COME..." Matthew 6:9
Now, why would Jesus tell them to pray that His Kingdom would come? Could it be that it was because He had literally just assured them that His Kingdom would come BEFORE THEY WOULD DIE?
Did you see the connection? He assured them it would. He made that promise to them. Not to us. To them. It was going to occur before they died. In that generation. Before THEY finished preaching in the towns of Israel. So therefore He told them to pray for it. Stay on the lookout for it.
God's will on earth would be as it is in Heaven. He would come and dwell in believers and His Kingdom would arrive. That all came to be at the end of the Old Covenant age.