--In the following you will notice that the reign is both in the past tense and in the future tense.
Rev: 20:4And
I saw the souls of those who had been beheaded because of their testimony of Jesus and because of the word of God, and those who had not worshiped the beast or his image, and had not received the mark on their foreheads and on their hands; and
they came to life and reigned with Christ for a thousand years.
5The rest of the dead did not come to life until the thousand years were completed. This is the first resurrection.
6Blessed and holy is the one who has a part in the first resurrection; over these the second death has no power, but they will be priests of God and of Christ, and
will reign with Him for a thousand years.
--First resurrection:
John 5:25
Matthew Poole's Commentary
The dead shall hear the voice of the Son of God: some understand this concerning the special resurrection of such bodies as Christ raised while he was upon the earth from death to life, of which number was Lazarus and the daughter of Jairus, &c. Others understand it of the general resurrection, spoken of
John 5:28,29. That which favoureth this sense is, because here is no mention of believing, but only hearing a voice. But the most and best interpreters rather understand these words of those who are dead in trespasses and sins, and the quickening and life mentioned
Ephesians 2:1, which is called the first resurrection,
Revelation 20:5, because of what was said immediately before, that such a one is passed from death to life; and what was said before, He that heareth my word, agreeth with what is said here of hearing the voice of Christ; and what followeth seemeth better to agree with this sense. And
John 5:28,29 speak plainly of the second and general resurrection of the body.
They that hear shall live; those who so hear the voice of Christ in the gospel, as to give a firm and steady assent to it, and, upon the credit of it, shall receive Christ as their Mediator and Saviour, shall live eternally; they do live the life of grace, and shall live the life of glory.
--Reign with Christ:
Matthew 19:
28And Jesus said to them, “Truly I say to you, that you who have followed Me,
in the regeneration when the Son of Man will sit on His glorious throne, you also shall sit upon twelve thrones, judging the twelve tribes of Israel.
--So, when is the regeneration? Clearly when He ascended on to His glorious throne and poured out the Spirit at Pentecost expressed in the following.
Titus 3:
5He saved us, not on the basis of deeds which we did in righteousness, but in accordance with His mercy, by the washing of
regeneration and
renewing by the Holy Spirit, 6whom He richly poured out upon us through Jesus Christ our Savior,