I think this is the first time I have tried updating my nuvi 2597 which I have had for about 9 months. When I connect to Mac and start Garmin Express it lists several available updates but fails to update citing the error "We cannot install the update because the SD card is locked". (see attached image).
What version of Garmin Express are your running? Can you make sure Express is up to date See FAQ: How do I update Garmin Express? If you have no SD card in the device the error you are getting is very strange. Try unplugging any other peripherals from the Mac then delete the device from Express and re add it. If this makes no difference uninstall and reinstall Garmin Express. If the error persists please contact product support.
