Is ignorance of the existence of the awaited Mahdi's narrations excusable, or is one held accountable for it?

It was previously explained when ignorance is excused and when it is not. The hadiths about the appearance of the Mahdi are not among the matters that most people are knowledgeable about; rather, ignorance of them is widespread. Therefore, whoever denies his appearance due to the evidence not having reached them, it is hoped that they will be excused for their ignorance. However, since the hadiths have reached you and you have believed in them, this is sufficient.