Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
That problem sounds like it was very alarming for you to encounter. I hope I can provide advice that will help with it.
In a Garmin device, when a portion of a map that is supposed to be there, becomes unavailable when you cross into some sub-area, then either
1. the map file has become corrupted, or
2. the operating software of the Garmin device has become corrupted, perhaps.
So repairs to either the map file, or the Garmin device's operating software, would probably fix the problem.
Try connecting the Garmin device in question, to a computer that is already running Garmin Express and has an internet connection 'live' at the time. Update the device with the Garmin Express software, and it might be fixed, perhaps.
To simply download, install, and use Garmin Express, go to
and (if you have a Windows PC) click on the big blue Download button at center bottom of the page. (If you have an Apple, click on the nearby Download for Mac link.)
And download Garmin Express' installer to your computer, save it, then double-click upon it to install Garmin Express.
Then start the program, Garmin Express. Then connect your Garmin device. Then use Garmin Express to update your device.
Let me know, by the Reply To Expert function, how this process goes, please. Thanks.