Is there no lighting up at all, no brief flash of the Garmin logo, no lights?
When you try connect to your computer do you get any indications at all? Does the computer see the unit at all?
I am afraid this unit has an internal fault... You can try a reset, if your unit has no recessed reset switch on the bottom then the only way to reset is to hold the power switch on for 8 seconds...
If no luck then it will need a serviceman, the best option is to send it to Garmin..
(for all Garmin products except Apollo aircraft)
Monday - Thursday: 8 AM - 6 PM, Friday 8 AM - 5 PM Central Time (closed holidays)
US:(NNN) NNN-NNNNbr />US Toll Free: 1-800-800-1020Canada: 1-866-429-9296
Sorry the news is not better
Sorry, but if the reset doesn't get the unit working again then there is no way to reload the unit software or do anything else. The unit has to be dismantled and with this model that is quite tricky, once dismantled you need to check the cpu board connections....
If you want to try dismantling the unit there are a number of videos on youtube that show how to do this... I can direct you to them...