Connect the camera to the Mac via the USB cable. Make sure you haven't inadvertently swapped your USB cable for a USB "charging" cable (many devices such as phones use these and ONLY the power pins are wired... the data pins are missing so it's not possible to transfer images if you have the wrong cable -- even though the cable will fit into the camera.)
After the camera is connected, power it on.
On the Mac, click the black Apple icon in the upper left corner of your screen and on the pull-down menu pick "About this Mac".
On the window that opens, pick "System report..."
This will launch the Mac's "System Information" utility.
In the left side margin of the System Information utility window, there's a hardware section with a "USB" category. Pick "USB" in that list.
On the RIGHT side of the window, it will display a list of all USB connected devices. It is important to recognize that it only does this scan for devices when the utility is launched. If you connect the camera AFTER launching the utility then you have to select "File -> Refresh Information" to cause it to rescan for devices.
If your camera shows up on that list, then the Mac can see the camera. If not, then then I'd probably test a different USB cable.
An SD card reader (and depending on which Mac you own, you may already have one of these) is typically the faster and easier way to transfer images.
If your Mac doesn't have a built-in reader, then you can get an external reader. I've gone through several low-cost readers and found them to be rather flakey. I ultimately bought a reader made by Lexar and that particular reader has worked with no hassle on every OS and machine I've used. So now I just stick with that brand.
Tim Campbell
5D III, 5D IV, 60Da
