It's possible that the operating system may have blocked access to the 'Documents' folder.
Here is how to enable it:
1. On your Mac, choose Apple menu > System Preferences.
2. Click Security & Privacy.
3. Select 'Files and Folders'
5. Find AmpKnob on the list and click on the '>' character to expand the contents
6. Make sure the 'Documents Folder' item is checked (blue)