I’ve tried absolutely everything. Have you, really? “Absolutely” could be, in this case, a poor choice of words. You’ve tried everything you could, within your power and knowledge.
When you can’t see the forest for the trees, try consulting someone who is more experienced in navigating through dense forests or someone who has navigated this particular forest before.
Sometimes a problem refuses to go away, even after establishing that you’ve done everything humanly possible. Even though “absolutely everything” sounds (more than) sufficient, it’s relative to your (current) capabilities. Reach out and ask for a fresh pair of eyes to help you look through the forest.