Question: Can Satan fool a person into thinking they are saved so that they end up in hell?
Answer: That's a great question. Satan is (as far as we know) the most powerful creature in the universe and it is his desire to ruin and to confound God's plans whenever and wherever he can. Deception is his primary tool, and, if we look around, we can see that he's doing a bang-up job, because relatively few people care anything about the Kingdom of God. The vast majority of individuals live self-focused lives, and even the majority of churches care nothing for Christ in real terms. So, how did the world get this way? Through poor management—Satan's, not God's. God is currently allowing Satan to run the show here on Earth, so think of him as the CEO of the world—except with superpowers!
“In their case the god of this world has blinded the minds of the unbelievers, to keep them from seeing the light of the gospel of the glory of Christ, who is the image of God.” (2 Corinthians 4:4, ESV)
“in which you once walked, following the course of this world, following the prince of the power of the air, the spirit that is now at work in the sons of disobedience—” (Ephesians 2:2, ESV)
Left to our own devices we are no match for Satan. He is god-like, and he is the power behind all evil. What this means for your question is, since Satan is in charge of daily operations here on Earth, if he is not the direct cause of any particular mayhem, he is the direct source of its power. But either way, he is always its administrator. This is why my initial answer to your question is, Yes, Satan can fool a person into thinking that he is saved. He will mount any deception, even within an earnest Christian fellowship, to make a person feel or think that he is going to heaven when he is not. That is the very definition of diabolical. But Satan is not the only show in town. The Bible teaches us that there are two other enemies besides Satan: the world and the flesh. Either of these might qualify as roadblocks to true salvation. People who focus on the world or upon themselves have the greatest chance of missing the will of God.
“Do not love the world or the things in the world. If anyone loves the world, the love of the Father is not in him. For all that is in the world—the desires of the flesh and the desires of the eyes and pride of life—is not from the Father but is from the world. And the world is passing away along with its desires, but whoever does the will of God abides forever.” (1 John 2:15–17, ESV)
Here's a scenario that fits your question. Let's say that there is this person who has been attending church for decades, and he thinks that he is right enough with God to get into heaven. Even if that man were the humblest acting person on earth, his position before God would be one of pride, and if he did not humble himself before God by repenting of his sins and turning to Christ, he'd surely go to hell. And if he did, then Satan could only take part of the credit, because the immediate cause of his failure would be the flesh (his pride) and not Satan. However, in his position as the CEO of evil, Satan could have orchestrated any number of ploys to let this man think this way. We can never know for sure. But either way, Satan could still take a bow as the manager.
Now that we know that he is not always the immediate cause of deception, let's refocus on Satan as the primary cause. One need not be a Bible scholar to see that Satan ruins lives. He has ruined them throughout all time and has ruined them in every nation. He ruins them today and hopes to ruin them in eternity. At some level, Satan is the cause of all grief, and it is this—this global effectiveness—that drives my yes answer. However, when it comes to Satan's effectiveness in deceiving the individual upon whom God is working, I am much more spiritually optimistic, and here's why.
God is active in drawing all people to himself (John 6:44). He wills that none should perish (2 Pet. 3:9). His Holy Spirit woos, Christians pray, the Gospel is proclaimed, and Satan cannot, by direct methods, defeat all of this spiritual positivity. The problem for us, of course, is that Satan does not use direct methods…and God does not make robots. We are volitional creatures, and as such, we have the creature's right to listen to Satan's patter rather than to God's still small voice. The result is that we can choose to snub God. But even if Satan himself whispered in our ears that we should ignore God, the decision to do so would still be ours. Satan has no power in these matters—not unless we give it to him. You can see how the full answer to your question is beginning to lean a little more toward a no than to our previous yes, so let me clarify: Yes, it is possible...but no, Satan does not ultimately deceive us. Ultimately, we can only deceive ourselves.
I must admit, though, that Satan is a huge problem. A question like yours might not have even come up if he kept his business in barrooms and brothels...but he comes right into our churches! And not just occasionally. He has better attendance than most believers! But he's not the only show. We can be deceived by our own personal pride or by our entanglement with the world and its systems, and I think that the immediate cause can vary among the three. However, no matter which of the contributing causes queue up against us, no one sends anyone else to hell. People decide to go there themselves...and there are no exceptions.
So, yes, Satan can fool a person into thinking that they're going to heaven, but no—it's not a lock...not as long as there's life.