Cannot execute boolean operation http://pasteall.org/blend/index.php?id=50320

I am using the testing ring as the difference (what I am removing) 

The plane (haven't got to naming it) as the subject (Be removed from)

It won't let me use the modifier. I have tried recalculating the normals I have also tried it without the face in the center of the testing ring extruding the bottom face of the plane and and the testing ring by zero

Would appreciate the help! 

https://imgur.com/a/v1CeG6H
Boolean modifier works with volumes, It will not work with 2D shapes, flat forms, one-sided geometry.

So first, you need to add some volume to your object:



So, I guess, you have a trouble with proportional editing is on, turn it off by pressing O and move one face up to make a volume. And select all and press Ctrl+ N just to make sure, that normals are correct.

Then edit a ring. Remove central faces inside the ring and add 2 face on top and the bottom like this:



This makes you boolean works.