Open your Chrome browser.
Tap the three dots in the top-right corner of the screen, hover over "More Tools" and then select "Clear browsing data"
Or Press CTRL-Shift-Delete on some models
Select the time range from the dropdown menu at the top, and choose which (if any) parts of your data you don't want to clear (browsing history, cookies and other site data, and cached images and files) by unticking the box next to the corresponding selection.
Click "Clear data."
Then restart your Chromebook.