Cannot access preference pane in system preferences to access iCloud

How to I get a preference pane to load?

I got the notice that iCloud account is running out of memory. I wanted to buy more memory and went to system preferences. I get the message "could not load iCloud preference pane."

I have tried restarting my computer. When I checked the knowledge base the only reference I could find referred to screen saver and to update my OS version - I'm fully updated.

Thank you for your help,

Jean

MacBook Pro mid 2009, 15 in, 10.11.5, 4 GB,