Which software are you attempting to use and what version do you have?
If you use the Canon utilities, download the latest software from the Canon support site:
https://www.usa.canon.com/internet/portal/us/home/support/details/cameras/dslr/eos-5d-mark-iii
Canon utilities don't check for updates, so what tends to happen is you have an older version of the software (possibly the version that was pacakged with the camera) and Apple has updated the OS one or two times (requiring new updates).
You don't have to use Canon's software. While i have Canon's software installed, most of the time I just insert my memory card into a card reader (I use the Lexar brand card reader that has both a CF card slot and an SD card slot) and use the card reader to import images (it's faster than importing from the camera over USB.) I then use Adobe Lightroom to import those images from the card into my LIghtroom library.
Tim Campbell
5D III, 5D IV, 60Da
