Adobe has posted this recommendation and warning regarding attempting to run older versions of Photoshop CC with High Sierra: “Adobe strongly recommends that customers update to the Photoshop CC 2017 release prior to updating to macOS 10.13 (High Sierra). Older versions of Photoshop CC were not designed, nor extensively tested to run on macOS High Sierra. Additionally, we strongly recommend that customers do their own testing on a non-production partition to ensure that new operating systems work with their current hardware and drivers (printing, etc). You may wish to remain on an older version of the OS that is compatible with prior versions of our software.”

Photoshop (CC 2017 or earlier) will fail to enter full screen mode if the Dock is shown.  This problem does not occur if the Dock is set to “automatically hide and show”.  This issue will be addressed in a future Photoshop CC 2017 update, and Adobe has workaround posted here.