Can a person who feels that God has sealed their heart due to committing major and minor sins return to God and repent?

Nothing stands between a servant and repentance, and Allah accepts repentance for every sin. Hearts are between two Fingers of the Most Merciful; He turns them as He wills, softening the hard and giving life to the dead. Allah Almighty said: (Has not the time come for those who have believed that their hearts should become humbly submissive at the remembrance of Allah and what has descended of the truth? And let them not be like those who were given the Scripture before, and a long period passed over them, so their hearts hardened; and many of them are defiantly disobedient) {Al-Hadid:16}. Then He said: (Know that Allah gives life to the earth after its lifelessness. We have certainly made clear to you the signs, that you may reason) {Al-Hadid:17}, to indicate that Allah softens hearts after their hardness and guides the perplexed. Just as He gives life to the dead earth with rain, so too does He guide hard hearts with the proofs of the Quran.