Replacing 3-way switch with Dimmer, no power

[webberb]

I'm replacing an existing 3-way switch with a 3 way insteon dimmer setup. I've done this before in a few different other areas of my house with no problem, so I have a bit of experience with the process and the setup. But with this particular installation, it does not work. Problem I see is that even though I find the switch box that has line (hot) coming in and I connect the switch to line and nuetral (which should then power the switch on, i.e. the green LED light light shoudl be on), it is not one. Like it it is not receiving power? I've checked the box for voltage with a meter, and (maybe becasue of the age of my house), the voltage doesn't quite come up to 120V... it's around 118V. Would this type of underpower situation cause the switch to not even power on?

any ideas on how to further troubleshoot? (it's not the switch as I've tried multiple switches in that location and get the same result).

[BLH]

No 118 volts is well with in the tolerance of the dimmer.
Try measuring the voltage with all the loads disconnected. It sounds like the white wire you are using is not a neutral but maybe part of a switch loop and you are reading back through the load.

Is there any black mark or tape on the white wire?

[stusviews]

In any 3-way configuration at least on white wire is not a neutral. Often, black is not line. Describe the wires in the switch box.