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Why Does My Descent Mk2 Series Watch Not Appear as Drive on My Mac Computer?

Garmin watches that feature Music storage, like the Descent™ Mk2 smartwatch, use Media Transfer Protocol (MTP) mode when connecting to a computer. This USB mode allows for the transfer of media files to the watch. Mac operating systems (OS X, macOS Sierra, and macOS High Sierra) only provide limited native support for MTP devices, which means these watches will not be recognized as external drives. 

NOTE: Garmin watches that use MTP mode can only be recognized by one application at a time. If you happen to have more than one Garmin application open, such as BaseCamp™ or Garmin Express™, only one will recognize the watch.  If you are having issues with another program detecting your watch, try closing any other Garmin programs that you might have open on the computer.