Is the repentance of one who wears an amulet accepted, knowing that he did so out of ignorance of the ruling regarding its polytheistic nature, then repented to God after learning the hadith: "Whoever wears an amulet has committed shirk (polytheism)"?

The duty was not to hang an amulet, for hanging it is disobedience to Allah and could be major or minor shirk. Whoever repents from any sin, even if it was shirk that takes one out of the fold of Islam, Allah accepts his repentance; because Allah says: "Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.'" The verse was revealed concerning polytheists who repented. And Ibn Kathir said: "This is general for all sins, including disbelief, shirk, doubt, hypocrisy, murder, transgression, and other things: whoever repents from any of that, Allah accepts his repentance." As for the saying of Allah: "Indeed, Allah does not forgive association with Him," this applies to those who die upon shirk without repentance. Since you have repented from hanging the amulet, we hope that Allah accepts your repentance.