Part of the problem here is that Canon is not consistent, and does not follow normal conventions, in their file name suffixes.
The original Canon RAW file was .CRW (Canon Raw). This was changed to .CR2 (Canon Raw Version 2). Then the trouble starts. The CR2 format has been changed. You'd expect therefore to see a new suffix each time the file format changed (e.g. CR3, CR4, ...) but unfortunately Canon kept the CR2 suffix. So now Canon RAW files with a .CR2 suffix can have different formats. Hence image processing software can successfully process some files but not others.
Regarding keeping up-to-date with file formats, Adobe does not seem great. Often you have to "update" LightRoom/Photoshop/ACR to handle the new formats. That in turn can force you to install a later version of your operating system which in turn might need a new computer! [You could imagine that everyone involved in Hi-Tech industry is in a conspiracy to force us to spend small fortunes in this way].
I have found that Iridient is much better at handling the most recent RAW files, and also tends to run on older versions of Operating Systems than Adobe tools. For example there is a version of Iridient that runs on OS X 10.6.8 (Snow Leopard) whereas most other recent software demands OS X 10.6.8 or later, and many Mac users see anything after Snow Leopard as a downgrade!
The important point is that at the time of writing (mid-2016) Iridient copes with all versions of .CR2 up to the latest in the G1x mark ii. I believe the differences are due to the G1x ii's ability to create images in a variety of aspect ratios.
Users of Sigma's cameras might like to know that Iridient is also one of the few developers that can process X3F files ... the RAW files from Foveon's Merrill chip (I cannot say whether it handles the Quattro formats). It is more stable, faster and generally nicer to use than Sigma's own SPP software and, in my opinion, it also makes a better job of them, especially in avoiding blown-out highlights. Adobe did process X3F files from the earliest Foveon chips, as in the original DP1 and DP2 cameras, but have never added support for the DP1/2/3 Merrills, the SD1 Merrill, or the Quattro cameras, and probably never will.