Sorry, I dont have the answer right now. I have the same monitor and problem.
I have been searching for the same answer.
So far I only have theories of a solution.
1.) A transistor on the monitor board has gone bad do to heat (and like all hardware we gullible Americans buy, they are only designed to last for a few years, and priced just right that we buy them repeatedly.)
And when I do have the answer, I will be certain to post my answer.