I just tested this and I'm able to toggle that checkbox on and off and save my changes.
When do you get the message? When you check the box or when you press save?
I don't know if LDS church membership has to do with this, but as an idea, click on the Membership tab (on the left) and make sure a membership number is listed and that it is correct.
Perhaps it's dependent on setting up your talents. I'm not sure what it's looking for, but you might look at Contribute Through Service. I don't see you listed as having signed a Individual Contributors License, but the other poster has. So that seems like a good place to start.
Have you searched the Help Center? Try doing a Google search and adding "site:churchofjesuschrist.org/help" to the search criteria.
So we can better help you, please edit your Profile to include your general location.