Hopefully your DMT just needs a good cleaning the diamonds clog up.

With some powdered cleanser, I use Barkeepers Friend, scrub the diamond plate face with a stiff brush, I use a Bix Stripping brush from Home Depot. It is like a large 1.5 X 2 in very stiff nylon brush. A couple of good scrubbing may revive it.

If not it may be trashed, always lap under running water or in a water pond.