What should a person do who was born with a name that is impermissible to use, and is now fifty years old, and it is difficult to change it? And is he sinful for that?

The names of Allah are divinely ordained (Tawqifiyyah), and the name "Al-Sattār" (The Concealer/Coverer of sins) has not been mentioned in the Quran or Sunnah. Therefore, it is not one of Allah's names. Consequently, it is not permissible to be named "Abdul-Sattār" or anything similar that involves servitude to a name which is not among Allah's names. However, there is no harm in being named "Sattār" without the prefix indicating servitude. As for the name "Jabbār" (The Compeller/Restorer), there is no harm in being named it because it is one of the shared names that can be applied to both Allah and others, and the pious predecessors (Salaf Sālih) were indeed named with it.