Honestly, in most of the places I hunt birds gobble much less than they did 10-15 years ago. I know they are there, but they aren't nearly as vocal as they used to be. I have a couple theories of my own, but nothing I want to put out here.
As far as making them gobble? Good luck, maybe an air horn or coyote call right before sunrise will get you a shock gobble or two. But that's the only trick I can think of. Like mentioned before, hunt them like deer, nowhere near as fun as calling in a screaming gobbler, but sometimes you have to make lemonade when life hands you lemons...