Magellen RoadMate 700 will not power up

I have had that problem. I believe the Magellan cradel design is defective. I expect it is not making contact and you need a new one.
BUT . First.
you need to know if you cord is OK.
is th elight on the end that plugs in.
use a volt meter to test to see if DC voltage is coming out the tip that
plugs into the GPS. ( sombody at Radio Shack might check the
ohms ( continuity of the cord . or you can do it with a light bulb, a 1.5 v battery and a wire. (one end of battery to tip of plug in .other end of battery to wire ,. other end of wire to each part of the cig lighter plug in.
if light comes on, that wire is OK . then check the other part of the
tip to the other part of the connector.
If the cord is OK>
Plug it in again in the car.. Wiggle the cord to make sure one of the
wires isn't almost broken so it works and then when bent , does not.
then wiggle the cradle , maybe reinstall the cradel.
the Whole time , you must turn on the power button on the GPS
each time you try something .If the button is off, you can have everything right and nothing will happen.
If it is the cradle they are about $15 on e-bay. There are a lot of them
that's why I think there is a problem.20 people would not be selling them unless there was a big demand.

if your sure its charged,(is the green light on the car charger) hold the power button for upto 15 seconds till it starts.