This article concerns using the SL MKIII script with Logic - which you can download here: https://customer.focusrite.com/sites/customer/files/downloads/novation-sl-mkiii-logic-plug-in.pkg_.zip 

You may find an issue in the InControl mode where the dials appear on the SL MKIII's screens but the parameter values do not reflect on the unit. This can be corrected by following these steps: 

1. Turn off the SL MkIII
2. Exit Logic Pro X
3. Open Finder
4. Press Shift + CMD + G
5. Navigate to ~/Library/Preferences/
6. Delete the file 'com.apple.logic.pro.cs'
7. Restart Logic Pro X
8. Turn on the SL Mk III

If you are still having issues please try reinstalling the Logic Script by using the installer.