Some changes in OSX 10.9 (and later) require some extra steps to enable scrolling capture.
- Open System Preferences
- Click Security & Privacy
- Click the Privacy Tab
- Click the Accessibility section
- Click the Lock button in the bottom left-hand corner and enter your administrator password if required
- Check the box next to Snagit under the “Allow the apps below to control your computer.”
- Quit Snagit, and relaunch.
- In Snagit, browse to the menu bar item Snagit > Preferences > Capture tab, and make sure scrolling in applications is enabled now.