In some cases it is necessary to manually set the security options on your Mac to allow the GPS update software to access the GPS files.
1. Open up System Preferences.
2. Select Security & Privacy.
3. Select the Privacy tab at the top, then select Files and Folders from the list, and finally check the Removable Volumes checkbox under the Lezyne Icon.
If you are still having trouble with this process, please submit a request.