Is a Muslim considered sinful for not inviting Christians to Islam, and are Muslim scholars accountable for those among them who died in disbelief?

The call to Islam is obligatory upon the entire Ummah and every individual according to their capacity. In this ruling, men and women are equal. A woman who possesses knowledge must engage in da'wah (calling to Islam) and guide towards good according to her ability, based on the words of Allah Almighty: "Invite to the way of your Lord with wisdom and good instruction" (Quran 16:125), and His saying: "Say, 'This is my way; I invite to Allah with insight, I and those who follow me'" (Quran 12:108), and His saying: "And who is better in speech than one who invites to Allah and does righteousness and says, 'Indeed, I am of the Muslims'" (Quran 41:33). Adherence to the Shari'ah guidelines is required when inviting disbelievers, and one must not speak without knowledge. It is preferable for women to invite women and for men to invite men.