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Perhaps you need to try using a different program first.
When dealing with an update for your Garmin device, it is best to simply download, install, and use Garmin Express.
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.
Then see if that helps with the My Garmin program also. It may well be just what the situation needs. If not, then check that your map type is still sold anywhere... even a site you do not want to visit nor use... just to make sure the map is not genuinely no longer issued nor updated. (Check the version of map offered, too, to make sure it is indeed newer than the one on your Garmin device, of course.)