Since no one went to heaven before Jesus opened the way for his elect to follow,
Enoch went to Heaven (3rd), for God (Jesus) took him, and he was no longer found on earth.
Scripture cannot be broken (John 10:35).
Therefore since Genesis 5:24 and Hebrews 11:5 say that Enoch was "translated" so that "he should not see (experience) death", and he "walked with God" and "he was not" (found on earth again, context), he was taken to Heaven (3rd), then John 3 cannot contradict those verses, or teach an opposing understanding. We must read John 3, in it's proper context, and Enoch (and/or Elijah), is not a part of that context.
Consider the context of John 3. Jesus is not saying that no one (person, human) had gone up to Heaven. Read the whole sentence, carefully, in the context of the sentences before and after it.
Consider the context of the verse cited please. Jesus did not say in John 3 that no one entered Heaven. He is speaking to Nicodemus, about being born again from Heaven, and about the doctrine/practice of Heaven itself. The context of the verse shows that Jesus is speaking about that no one went up to Heaven to obtain the doctrine (and way of Life) and return, but instead it took an act of God, to descend from Heaven to bring with Him the doctrines/practices of Heaven. In other words, it took the condescension of God to uplift fallen mankind, and elevate them.
John 3:12 If I have told you earthly things, and ye believe not, how shall ye believe, if I tell you of heavenly things?
You see, the Son of Man (Jesus) came down from Heaven at the behest of the Father, and by His own will in 'Amening' the Father, and brought with Him the ways of Heaven, of which carnal and earthly man could never have known on their own, for their hearts always tended downward, never upward. The earthly and carnal man could not even conceive of Heavenly things, unless Christ Jesus came down to tell them of it and show it to them in word and in deed.
Enoch, Moses and Elijah all were in Heaven (3rd) already, as scripture declares (cited previously).
Most people incorrectly think it reads, "No man hath ascended up to heaven.(period)"
But that is a misreading or misquotation of the text. It is taken out of context, and ignores the previous sentences, along with the connecting "kai" (and; vs 13), and the fact that there is no period after "Heaven", but instead a continuing thought that connects to the previous verses. Look again please.
John 3:12 If I have told you earthly things, and ye believe not, how shall ye believe, if I tell you of heavenly things?
John 3:13 And no man hath ascended up to heaven, but he that came down from heaven, even the Son of man which is in heaven.
Here is the koine Greek, as needful:
John 3:12 ει τα επιγεια ειπον υμιν και ου πιστευετε πως εαν ειπω υμιν τα επουρανια πιστευσετε
John 3:13 και ουδεις αναβεβηκεν εις τον ουρανον ει μη ο εκ του ουρανου καταβας ο υιος του ανθρωπου ο ων εν τω ουρανω
The "kai" completes the thought from vs 12, which continued from vss 1-11, for instance, "no man can do these miracles (which originate from Heaven" (vs 2), "born again", "kingdom of God" (vs 3), "born again", "Spirit", "kingdom of God" (vs 5), "born of the Spirit" (vs 6), "born again" (vs 7), "the wind", "born of the Spirit" (vs 8), "How can these things be?" (vs 9), "these things" (vs 10), "we speak that we do know, and testify that we have seen; and ye receive not our witness (of Heavenly things)" (vs 11), "heavenly things" (vs 12), "eternal life" (vs 15) and further on into vss 16-21.
Read the context. He (Jesus) was talking about His spirit/mind/heart and where it always dwelled in (heavenly things, see vs 11), not His physical body/person, which was sitting right there with Nicodemus. It was a contrast of the carnal (Nicodemus) mind (vs 4) to Jesus' own mind (which is always dwelling on His Father in Heaven, always dwelling upon doing His Father's will in Heaven).
John 3:6 That which is born of the flesh is flesh; and that which is born of the Spirit is spirit.
Thus the "we" speak. This refers to Jesus and the Holy Spirit in the context, the Two (Great) Witnesses of the Father, which came from Heaven.
See also:
Colossians 3:1 If ye then be risen with Christ, seek those things which are above, where Christ sitteth on the right hand of God.
Colossians 3:2 Set your affection on things above, not on things on the earth.
Philippians 3:20 For our conversation is in heaven; from whence also we look for the Saviour, the Lord Jesus Christ:
Ephesians 2:6 And hath raised us up together, and made us sit together in heavenly places in Christ Jesus:
Romans 8:5 For they that are after the flesh do mind the things of the flesh; but they that are after the Spirit the things of the Spirit.
Romans 8:6 For to be carnally minded is death; but to be spiritually minded is life and peace.
Romans 8:7 Because the carnal mind is enmity against God: for it is not subject to the law of God, neither indeed can be.
Philippians 2:5 Let this mind be in you, which was also in Christ Jesus:
Isaiah 26:3 Thou wilt keep him in perfect peace, whose mind is stayed on thee: because he trusteth in thee.
The entire context is not about anyone not simply entering Heaven. The entire context is about Heavenly "things", and that no man (no one) went up to heaven to obtain those things and bring them back down (for the carnal mind could not even conceive of Heavenly things) , but rather, God (the Father, vs 16) sent the Son from Heaven, and He descended with those things for mankind who needed them, and could obtain them no other way and could speak about them to Nicodemus.
Ephesians 4:9 (Now that he ascended, what is it but that he also descended first into the lower parts of the earth?
Ephesians 4:10 He that descended is the same also that ascended up far above all heavens, that he might fill all things.)