Hello & Welcome to Just Answer,
Sorry to hear of any issue you are having with your device.
To help you with this issue, may I ask:
1) The FULL Model Number of the device you are working with? You SHOULD be able to find a label or sticker on the BACK of the unit, that has a 4-digit number right after the word "Roadmate".
2) Can you guess at when the device was last used?
3) How long was the device connected to power AND is there ANY "indicator" on the power adapter that might suggest if it is working (providing power)?
Once we know the model, we may be able to judge if it would be worth it to repair or whatever - to get it working again.
I just wanted to check up and see if you had found the model number of this device yet.
I look forward to your reply here.