Garmin Is Recognized by the Mac but Not by BaseCamp
Other programs may be actively communicating with your device while it is plugged into a computer. Try closing out other Garmin applications that may be reading your device.
Example: If Garmin BaseCamp is not seeing your device, but Garmin Express is, close Garmin Express.
If other programs are not interfering, try the following:
Ensure That Garmin BaseCamp Is up to Date
Click Garmin BaseCamp in the menu bar.
Click About Garmin BaseCamp.
Click Check for Updates to Garmin BaseCamp. NOTE: If the Garmin BaseCamp program is running the latest version, Check for Updates will not be an option.
If there is an update available, click Install Now and follow the prompts to complete the update.