Hello & Welcome to Just Answer,
Sorry to hear of any issue you may be having with your device.
When I look up that Serial Number (starting with GK), that tells me that this is a TomTom XL 350, AND that the "TomTom HOME" program should be used to get any updates that are available for the device.
So let me give you a link to where you can get the LATEST version of TomTom HOME loaded onto your computer, then you should be able to run that program and connect the device (via USB cable) when instructed, and then perhaps update the device.
NOTE: It is recommend that the device be FULLY charged before starting the update process.
Click here --> Software for TomTom update.
Once on that page, click on the TomTom HOME icon, and then download the Mac version of the program.
NOTE: There are instructions on that page once you click on the TomTom HOME icon.
Please give that a try and let me know if you have any issues with that process.
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Thanks, ***** *****