In a recent question, it was pointed out that you couldn't sneak attack an invisible opponent because the rules specifically state that you cannot have disadvantage for the attack. However, it would not be impossible for the rogue to also have advantage on the attack, by virtue of being hidden or invisible himself.
In this context, where a character has both advantage and disadvantage on a single attack/check, the rules mention that the roll is resolved normally: you roll a single d20 and that's it. Does that mean that you are no longer considered advantaged/disadvantaged? If so, and assuming the presence of an ally within 5ft of the invisible enemy, it could mean that an invisible rogue could sneak attack an invisible opponent while a visible rogue couldn't. Or are you, in fact, still considered both advantaged and disadvantaged, and thus can't perform a sneak attack?
Precision: Sneak attack is the use case that triggered the question. That being said, there are probably other things that require advantage/disadvantage to be activated, so answers should focus on the relationship between advantage and disadvantage, and not on sneak attack necessarily.