Those who don’t believe do it out of lack of information and can still be convinced otherwise but those who reject do it with the knowledge they have of a subject.
John 12:47-48 And if anyone hears My words and does not believe, I do not judge him; for I did not come to judge the world but to save the world. He who rejects Me, and does not receive My words, has that which judges him-the word that I have spoken will judge him in the last day.
Thomas did not believe Jesus but later changed when he saw the wounds and touched it. John 20:26-28 And after eight days His disciples were again inside, and Thomas with them. Jesus came, the doors being shut, and stood in the midst, and said, “Peace to you!” Then He said to Thomas, “Reach your finger here, and look at My hands; and reach your hand here, and put it into My side. Do not be unbelieving, but believing.” And Thomas answered and said to Him, “My Lord and my God!”