I can see my images on import window, between they go through the import process I get an error saying that the images could not be imported. I just upgraded my camera to Canon 5D Mark IV. On import screen, images begin with "CR". When I click on an individual image, they appear very small.
Images begin with GR. I have tried importing through 5D, 6D, and through card reader with same result
What version of LR are you using?
If you have LR 6 or CC 2015 then update it to 6.7 from here.
If you have LR 5 then you will need to use the newest version of the free Adobe DNG converter program to convert those CR 2 raw files to DNGs before you import them.