"The Disk You Inserted Is Not Readable by This Computer" Error When Connecting a Garmin Device to a Mac

When plugging a mass storage Garmin device into the USB port on a Mac, the following error message may display:

The disk you inserted is not readable by this computer

This generally occurs when the device is not functioning correctly or when its internal memory is corrupt.

In Order to Resolve This Issue, Repair the Disk Using Disk Utility. 

1. Connect the device to the computer.

2. Click Finder.

3. Click Applications.

4. Double-click the Utilities folder.

5. Double-click Disk Utility.

6. Select the Garmin drive.

7. Click First Aid.

8. Click Run.

After the repair, the device should communicate properly with the Mac.