John 3:16-21 (KJV)
16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
17 For God sent not his Son into the world to condemn the world; but that the world through him might be saved.
18 He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.
19 And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil.
20 For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved.
21 But he that doeth truth cometh to the light, that his deeds may be made manifest, that they are wrought in God.
GOD made the way for everyone to be reconciled to Him.
To reconcile is (cited from https://www.thefreedictionary.com/reconcile):

1. To reestablish a close relationship between: reconciled the opposing parties. Because sin separates us from GOD, He made a way to again unify us with GOD.
2. To settle or resolve: reconciled the dispute. Because we rebelled against and disobeyed GOD, He made a way to resolve the enmity between us and GOD.
3. To make compatible, harmonious, or consistent: reconcile my way of thinking with yours. Because we where in the kingdom of darkness under Lucifer control in the world our thinking, understanding, perception was not in line with GOD but actually opposed it, He made a way to change our hearts and minds to we are now in the Kingdom of God and in line with His ways.

He did that because of His great and unsearchable love. Romans 8:38-39 (KJV)
38 For I am persuaded, that neither death, nor life, nor angels, nor principalities, nor powers, nor things present, nor things to come,
39 Nor height, nor depth, nor any other creature, shall be able to separate us from the love of God, which is in Christ Jesus our Lord.
This reconciliation, this salvation is not automatic but it is available to anyone.
As Jesus said that we have to believe in Him, Jesus Christ, believe in His name, Jesus Christ. Jesus Christ is the truth John 14:6 (KJV) Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me. and as it says in verse 21 when we genuinely believe it results in actually doing the truth, that is living the way GOD wants us to live according His standards, His ways,….
Some people choose not to believe because they love the kingdom of darkness and therefore sin more than GOD and thereby rejecting His salvation. Before we believe we are condemned already because all of us were born in sin and are citizens of the kingdom of darkness. When we believe, we become citizens of the Kingdom of God and that condemnation is removed by what Jesus Christ did on the cross as His blood makes us clean from our sin 1 John 1:9 (KJV) If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
In summary:
John 3:36 (KJV) He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him.
Therefore let us always call on Jesus Christ, put out trust in Him, believe in Him, resulting in living His way. Romans 10:13 (KJV) For whosoever shall call upon the name of the Lord shall be saved.