MacOS X 10.13 (High Sierra) and later implements a security feature in Snagit that affects the ability to install and utilize the TechSmith System Audio Capture kernal extension.
In order to use the TechSmith System Audio Capture Component, the extension needs to be allowed through the macOS X security settings.
Steps to enable the extension
- Open Snagit.
- Select Snagit > Preferences > Capture.
- Click Install Component.
- Open System Preferences.
- Click Security & Privacy.
- Select General.
- Click Allow at the bottom.
Try recording system audio in Snagit. You may be asked to install the system audio component again. If so, follow the steps to install it again, and then give it another try.