I believe that only Christians will be raptured.. and... if people did hear the gospel and denied it... or were spoke to about Christ and His saving grace and ignored it.... then they will have no second chance...
For those that never heard before, and on the rare occasion that they are "awakened" to the truth after the rapture, if it comes before all of the tribulation, then they will have the chance to turn down the mark, and be martyred...But.. that's just me.
I believe that God does not only give each person 1 singular chance to believe the Gospel, you can reject a gospel that you hear and still come to believe it later. People change. If you introduce Christianity to a young teen and they reject it, does that mean that 20 years later it's impossible for them to repent? No. Peter denied Christ 3 times in 1 night. He then repented when the [bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse] crowed.
My own testimony on this.
I was not raised by a Christian family, my first introduction to Jesus was when I was about 5 or 6 through the lady that ran my daycare. She tried to tell me based on the old testament, I knew Jesus was the Son of God, and God created the earth, but the message of salvation was lost because she taught a works based salvation, the importance of Jesus Himself was completely lost in the teaching because of the emphasis on works and obedience. What's the point of a savior if you're saving yourself according to theid doctrine? It didn't make sense. Also being that young, a lot of other topics simply did not make sense, praying for the end of the world and the world being destroyed by fire? Before you understand the resurrection, before you understand the new earth, before you understand the second coming of Christ, that sounds like a suicide pact! So yes I rejected their teaching, it didn't help that they abused me, so I saw whatever they were trying to teach as a bad thing because they were bad people.
I didn't come to Christ until I was about 12, and different circumstances happened then. I was friends with neighbors who were Christians and so first off, I'm much more willing to listen to what decent people have to say about Jesus than what people who would abuse me would say. Secondly they got me to go to vacation bible school over the summer, so that I could be properly taught the Gospel by people who knew what they were doing. It made much more SENSE when you realized that the reason we call Jesus the savior is not because He's just the son of God but because He actually went to bat for us and was sacrificed to atone for our sins. That made me realize the greatness and goodness of God where the prior teaching only managed to get through to me that God was just some mean guy in the sky smiting people for making mistakes. THAT is when I believed.
But you see, there are multiple factors at play.
1. The quality of the witness you received. Nobody is perfect, and if they are bad people trying to teach you anything, even a good thing, their teaching will be poisoned by their own shortcomings. The right teacher can be the difference between salvation and condemnation. So always strive to be a better witness when you try to bring others to Christ, their judgement of Christ and your teaching might be skewed because of their judgement of you.
2. False doctrines can muddy up a message to not make sense anymore If you teach an incorrect doctrine is it any wonder why someone would feel your religion makes no sense and rejects it but later converts when they hear better doctrine?
3. The age and maturity of the listener plays a big factor, if a young child or even young teenager rejects the message they just might not be ready for it and understand it yet. Give them time. Revisit the gospel when they're older, when they're more mentally mature and maybe their circumstances have changed. You know how many people converted after they hit rock bottom in their life?