Chev 2500HD - No trailer brake power at 7way.

Testing with a multi meter across the ground pin and the trailer brake pin at my seven way connector on the truck, I get no voltage when the prodigy P2 is manually activated.
Question number one… Is there a fuse on the truck that I should check?
Question number two… Am I Testing this properly? Or does the trailer need to be connected and check for voltage at the trailer?