If you are not able to get any light out of the dimmer whatsoever, then chances are that either the product wasn't wired correctly, or (and don't think I'm trying to be a **** about this, this was actually the answer on more than one occassion), the person using it didn't realize that you turn the dimmer on by pushing the knob in.
Answers & Comments
Grounding will not effect the issue.
If you are not able to get any light out of the dimmer whatsoever, then chances are that either the product wasn't wired correctly, or (and don't think I'm trying to be a **** about this, this was actually the answer on more than one occassion), the person using it didn't realize that you turn the dimmer on by pushing the knob in.