Anyone ever hear the story of the boy who cried wolf?
A boy was charged with watching the sheep to make sure that wolves wouldn't eat them. If he saw a wolf, he was supposed to yell, "Wolf! Wolf!", which would alert the adults for help.
Well for fun, mischief, boredom, or who knows what the boy decides to cry wolf when there is no wolf. The adults come, and seeing no wolf, they reprimand the boy.
Well, out of fun, mischief, boredom, spite, who knows what the boy decides to cry wolf again when there is no wolf. The adults come, and seeing no wolf, they reprimand the boy.
So every so often, the boy will cry wolf when there is no wolf, and eventually the boy is not taken seriously. One day an actual wolf comes, and when the boy cries, no one comes. Sheep were lost that day.
It might be the case that so much of what you say has been debunked in the mind of the other that they cease to take you seriously when you say something that is real.
And lets not kid ourselves, pointing out that the other side is dishonest doesn't magically undo the dishonesty of the side that is pointing.