Try wetting it first. And a new "feeder" (for wet food) can be as simple as a cat food dish or small pie pan or bowl. Work your way up from there. Hope you find a solution!
I'd put out a 2nd feeder, and I'd try a different food (just get a small bag since we don't know if they'll eat it), just to see if some change might encourage them. Make sure to check mill date on the bag to ensure you're getting fresh feed.
Or if you haven't tried it, maybe try fermenting a...