Josh,
Welcome to the forum.
What model of Denon receiver?
Please confirm, your orignial front right and front left speakers still work normally, and the only problem is the new center speaker not working.
If you push the stripped wire in a bit too far into certain connectors, when you tighten down the retainer, sometimes you end up catching plastic insulator--leading to no electrical connection and no sound.
- Double check you have a metal to metal connection on both ends with both wires (+ and -).
Cheers,
XEagleDriver