The 6D Mark II was first supported by 9.12.
Sounds like you have not installed the Camera Raw 9.12 update correctly.
In Photoshop, click Help > About Plug-Ins > Camera Raw to confirm which version you've got installed.
Thanks, already checked the camera raw version that photoshop is using and it appears to be correct.
If you've definitely got 9.12 installed and you've definitely confirmed that via Help > About Plug-Ins > Camera Raw, can you actually open 6D Mark II Raw files in Photoshop?
Yes, Photoshop will actually open a file. The problem is that I cannot see which image it is that I am opening. So, in photoshop I go file, open and then navigate to the file that contains the photos that I want to edit. All the images are listed in the folder but when I change the view to medium-sized or large icons to display thumbnails of the images I just get the raw icon (blue mountain inside a blue frame). For images taken with older cameras there is no problem seeing the image thumbnails.