Can a priest or a pope have invincible ignorance?

Invincible ignorance means that if you do not know something is a sin, you may not be guilty of that sin, because your ignorance cannot be remedied: you are not near anyone who knows the truth, you have not heard it from any teacher, you are not in a country that has knowledge of that subject. That is a rare situation. In our day it is very rare to find someone whose ignorance genuinely cannot be remedied; even in African countries, few are without knowledge of the Church and the Gospel, so the phrase loses its impact the further we go into modernity. In my opinion, although it may be theoretically possible in the extreme, it is practically impossible for a priest or a pope to have invincible ignorance. That would be my best answer: practically impossible.