Lightroom sometimes gives an error message “Cannot create required folder” or “An error occurred when attempting to change modules” referring to Application Support on Mac OSX with a file path:
/Library/Application Support/Adobe/Lightroom/Develop Presets
It is often due to incorrect permission settings and can usually be fixed by ensuring correct read & write permissions. Go to your user Library (substitute your own name for 99jon)
Macintosh HD >> Users >> 99jon >> Library >> Application Support >> Adobe
The easiest way to get to your Library is to launch Finder and on the menu click Go whilst pressing the Optn (Alt) key and then choose Library. By default the Library is hidden unless the Alt key is held down.
Click on (highlight) the Adobe folder and press Cmd+i to bring up the info dialog. Ensure you have read & write permissions. If not, click the padlock icon and change. Also check the permissions on the Lightroom and Develop Presets folders in the same way.
See image below.
Can’t see the user Library?
Click to enlarge
Sometimes the Develop Presets folders and others like Keyword Sets are completely missing from the Lightroom folder or were never properly created during installation of the software. Renaming the Lightroom folder will often fix the problem. A new folder will be generated on next launch.
Rename the Lightroom folder
Application Support >> Adobe >> Lightroom_OLD
Please also see this Adobe help document for other possible solutions and for Windows users.