Hello & Welcome to Just Answer,
Sorry I didn't see your question earlier and to hear of any issue you are having with your device.
To help you with this issue, may I ask:
1) The AGE of the device?
2) Has ANYTHING CHANGED - since the device was last used (such as vehicle its used in, location, etc.)?
3) WHEN this issue first began (or was noticed)?
4) If you power it up and let it sit on the MAIN screen, do you see ANY GREEN "signal bars" at the top of the screen?