Is it possible that the lack of success in performing Qiyam al-Layl for two days is due to a sin?

Sins are very dangerous and can be a cause of deprivation. However, sleeping through the night vigil (Qiyam al-Layl) may not always be due to sins; it could be a gift from Allah and a charity bestowed upon the servant.

It is recommended for a Muslim to intend to perform Qiyam al-Layl before sleeping so that the reward for what they intended is written down for them if sleep overcomes them. If one misses Qiyam al-Layl, it is recommended to make it up, as it was reported that the Prophet, peace and blessings be upon him, would make up his missed nightly portion (wird) between the Fajr prayer and the Dhuhr prayer.