Try updating Sierra. I am told the latest update has fixed this.
Also, do you have version 2.14.20a of EOS Utility installed? (Since you can't run it - you can look at /Applications/Canon Utilities/EOS Utility/EU2/EOS Utility 2.app in Finder and it should have the version info.)
If not, download the package from
https://www.usa.canon.com/internet/portal/us/home/support/details/cameras/dslr/e os-70d(choose El Capitan or Yosemite since they have nothing released officially for Sierra yet :- / )