A question can remain unanswered because it combines assumptions that do not belong together.

Some questions cannot be answered because they were badly built. They fuse two assumptions that do not sit together, and every attempt at an answer fails not from lack of evidence but because the question is asking about something that does not exist in the shape described. No amount of effort fixes a faulty premise.

If you have been stuck on the same question for a long time, take the question apart before trying again. What does it assume, and is each of those things actually true? Problems that resist for years often dissolve the moment someone notices that the wording contained a mistake.