Will Allah open a sealed heart?

Better to ask, “Can Allah open a sealed heart?” The answer is “Yes, He can” and it would be for reasons related to the person’s spiritual decisions or good deeds they have done, or some other reason resulting from their deeds which Allah deemed a good reason for unsealing their heart. This would explain why Allah may open one sealed heart and not all within the framework of Allah’s supreme justice.

As Allah Ta'ala is the most merciful the most kind, He will answer the dua’ of His slaves who are repenting to Him and asking Him to open their heart.

Allah the Almighty said:

“Has not the time come to the hearts of those who believe …… lest they become as those who received the scripture before …. And so their hearts were hardened!”

"Know that Allah gives life to the earth after its death!” [1]

It is to give hope that Allah can open the sealed heart which submits to Him and asks His help.

Reference:

[1] Surah Al-Haddid, 57:16-17