Mine worked using ADMIN as user name and Serial Number (9 characters-four letters and five numbers) that is inside the ink Chamber, below the cartridges in the bottom rail...
I had the same situation...my 5d3 won't open eos utility when connecting to my MacBook. The way i solved it was opening the app Image Capture that is default in Mac ...when it was open i could see my pictures...But the best part is that when i clicke...
