Question: "Why doesn't God give the fallen angels a chance to repent?"
Answer: The Bible does not specifically address the issue of God's giving the fallen angels an opportunity to repent, but we do know principles and can extrapolate from them an educated guess. First, Satan (Lucifer) was one of the highest angels, perhaps the highest (Ezekiel 28:14). Lucifer—and all the angels—were continually in God’s presence and had a complete knowledge of the glory of God, unobstructed by the things that keep mankind from knowing Him fully. Therefore, they had no excuse for rebelling against God and turning away from Him. For Lucifer and the other angels to rebel despite what they knew about God is the utmost of evil, and this most likely results in God's not giving Satan and the other fallen angels the opportunity to repent.
Second, God did not provide a plan of redemption for the angels as He did for mankind. The fall of the human race necessitated an atoning sacrifice for sin, and God provided that sacrifice in Jesus Christ. In that plan of redemption, God redeemed the human race and brought glory to Himself for His grace, love and mercy.
No such sacrifice was planned for the angels. In addition, God referred to those angels who remain faithful to Him as His “elect angels” (1 Timothy 5:21), and we know from the biblical doctrine of election that those whom God elects to salvation will be saved, and nothing can separate them from God’s love (Romans 8:38-39). Clearly, those angels who rebelled were not “elect angels” of God.
Finally, the Bible gives us no reason to believe they would repent even if God did give them the chance (1 Peter 5:8). The fallen angels seem completely devoted to opposing God and attacking God's people. The Bible tells us that one of the things God judges on is how much knowledge of Him a person possesses (Luke 12:48). The fallen angels, then, are even much more deserving of God’s wrath because of the exceedingly great knowledge they had about God.