It is possible that the fuse in the car charger has blown or the car female plug has issue and so its not charging your device.
You can confirm this by connecting it to your computer using the USB cord and charing it for 6-7 hours (running computer) and then try to start it.
Also, try to plug in your gps to some other car (using current charger) and see if it works there. If it does, then you know that its your car's issue.
The USB cable will look like this :
Can you please try this and let me know
Now, if you confirm that your car charger as well as car plug is fine, then your garmin has hardware issues and needs repair. If in warranty Garmin will repair it for free. Else first take a quote from them as it might be cheaper to buy a new unit.
Feel free to ask any question or concern you may have. I will be glad to help you.
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