If Allaah has sealed my heart for not praying three consecutive Jumu'ah, will he forgive me if I do Du'a'? I want to by heart some parts of the Qur'an--will it be accepted?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

Allaah has made Jumu'ah prayer an obligation on every pubescent Muslim male who does not have a sound and valid excuse not to attend it. Indeed Allaah ordained that we hasten to Jumu'ah prayer as He says (which means): {O you who have believed, when [the Athaan] is called for the prayer on the day of Jumu’ah [Friday] then proceed to the remembrance of Allaah.}[62:9]. The Prophet warned us against missing the Friday prayer without any sound and valid excuse as he said: "Some people should stop missing Friday prayers otherwise Allah will put a seal on their hearts and thus they will be among the heedless." Therefore, as you have missed some Jumu'ah prayers, you have to repent to Allaah and you should know that the Mercy of Allaah is vast as He says (which means): {But indeed, I am the Perpetual Forgiver of whoever repents and believes and does righteousness and then continues in guidance.}[20:82]. So you have to perform acts of good deeds as much as possible. Among these acts is to be keen on memorizing the Book of Allaah as the good deeds wipe out the bad ones. Indeed whoever sincerely repents, Allaah has promised to accept his repentance and change his bad deeds into good deeds.

Allaah knows best.