Screenshots taken with keyboard shortcuts in Simple Finder are not saved in a location that is accessible to Simple Finder users.
Solution
The system administrator can allow Simple Finder users to use the Grab Utility. This utility allows Simple Finder users to save screenshots in their Documents folder.
Allowing the Grab utility for Simple Finder users
2. Open System Preferences.
3. Choose View > Accounts.
4. Select the user.
5. Click Capabilities.
6. Allow Grab in the Capabilities list. (The checkbox is under the Utilities disclosure triangle.)