Mac App Store: "An unknown error occurred (100)" when purchasing
When attempting to purchase an app, an alert may appear indicating the app couldn't be purchased, as well as "An unknown error occurred (100)".
Try the following steps to workaround this issue:
- Quit App Store.
- Wait 10 seconds or more.
- Open App Store again.
- Navigate to the desired app.
- Click Buy.
If the issue persists, try restarting your computer and attempting the app purchase again.