If a Garmin watch displays the message Can’t Unlock Maps or Can't Authenticate Maps, it has detected a map that cannot be validated for use with that device.

This can be caused by:

A problem with the data in the map file
Incorrect or missing unlock information for an installed map

To resolve these issues:

If the issue occurred as a result of updating the maps, ensure that Garmin Express is up to date and reinstall the maps. Instructions for reinstalling maps can be found under related content. Be sure to use the Safely Remove Hardware option on a Windows computer, or the Eject Device option on a Mac, after the update has completed. Even though the update appears to complete, the write-caching feature on some computers may have not have completely built or transferred the map to the device. Ejecting the device before disconnecting it can prevent this error.¹
If maps have not been installed or updated recently, update the maps using Garmin Express.

The Garmin watch should now power on without displaying the error message. If you continue to receive the Can't Authenticate Maps error message, please contact Garmin Product Support for assistance.

¹To safely remove the device:

Windows: Press the Windows key + E, Right-click the Garmin device and choose Eject (if the device is not listed it does not need to be ejected)
Mac: Drag the device to the trash or select the Finder and choose the Eject symbol next to the Garmin device