Before saving the chapters of audiobooks, you need to set accessibility in Mac preferences. And setting accessibility in Mac preferences on Mac OS 10.9.x is different from Mac OS earlier. You have to check the settings as follows.
Section 1: Save the chapters on Mac OS 10.9.x or later
Click the app menu and select Preferences to customize the Chapters Settings. When you select the option Keep chapters, then you will see the following dialog popup.
Then click Open System Preferences button and click the lock icon to make changes in the Security & Privacy window. Then Select the Accessibility in the left side area and check the app checkbox on the Privacy pane.
Section 2: Save the chapters on Mac OS 10.8.x or earlier
When you select the option Keep chapters, then you will see the following dialog popup.
Then click Open Universal Access Preference button and check the Enable access for assistive devices checkbox in the Universal Access window.
1. The Keep chapters option only works on the original file with the chapters and the output has been set as AAC.
2. If you have already checked the Enable access for assistive devices checkbox, there will be no window pops up when you set Keep chapters option.