During System Boost while your Browser Manager is running you may get a result saying "Failed to get history" for clearing Chrome's cookies and history. This is because your Chrome application is still running.
You need to close Chrome entirely. When you click 'x' on the browser to close, it doesn't close down completely, and it is still running and sometimes hiding next to your clock in the system tray.
Press down Control + Alt + Delete and select task manager from the pop-up. From the active processes list, find Google Chrome, select them and click "End task" as shown below.
If your system allows it, you can also just hover your mouse over the system tray next to the clock, right-click and close Chrome. Once your browser is fully closed, rerun the scan and you'll be able to clear Chrome cookies and history.