After Effects CC won't open on Mac OS X.9

from:  known issues and workarounds for After Effects CC (12.2) | After Effects region of interest

After Effects fails to start on Mac OS with warning message about not being about to rename or move a file.

(This, too, isn’t actually an issue specific to After Effects CC (12.2); it affects every version of After Effects and a lot of other applications.)

In some cases, After Effects fails to start, giving a warning message like this:
“After Effects warning: Could not rename the file ‘/Users/USERNAME/Library/Preferences/Adobe/After Effects/12.2/Workspaces.numbers.xml’ to ‘workspaces.xml’.”

The warning might be about something somewhat different, but any message that says that a file can’t be written, overwritten, or renamed is likely caused by the same root issue:

This happens because Mac OS has incorrectly set the permissions for some files, preventing After Effects from writing and moving the files that it needs to operate.

One common cause of this problem is that when you upgrade a Mac OS (as opposed to installing the new version fresh), Mac OS will often set permissions of folders and files incorrectly.

To fix this in the case of After Effects, go to the preferences folder and set the entire preferences folder ( Users/USERNAME/Library/Preferences/Adobe/After Effects/12.2/ ) and all of its contents to be writable, not read-only.

Note that Apple hides the Library folder by default, so you’ll need to show the Library folder. See this page on the Apple website for instructions on setting permissions.