Will a person who owes a debt to Allah enter Paradise, and how will Allah hold him accountable for that, and will this debt be fulfilled in Hell, similar to making up missed prayers or fasting, or the non-acceptance of his prayer or fasting without his knowledge of the reason?

How reckoning occurs and entry into Paradise or Hellfire happens are unseen matters that cannot be known in this world. A Muslim must obey Allah's command and perform the obligatory duties. Whoever misses prayers or fasting due to an excuse (forgetfulness or sleep) must make them up and is not sinful. As for one who deliberately misses them, he is disobedient, and the majority of scholars oblige him to make them up immediately. Whoever neglects making them up and dies before repenting, his matter is with Allah. Ahl al-Sunnah (Sunnis) believe that whoever dies without associating partners with Allah will enter Paradise, even if it is after reckoning and punishment. Absolving oneself of obligatory duties takes place in this world, not in the Afterlife. As for the acceptance of acts of worship, its return is to Allah Almighty, and a Muslim must perfect them and perform them sincerely, while hoping for acceptance and entrusting the matter to Allah.