If Chromebooks are displaying a white screen, be patient – this means the testing servers are probably busy and the problem usually resolves itself.
Try the below problem-solving steps; if one doesn't work go to the next step.
1. Reload the page (Ctrl+R)
2. Wait a couple of minutes, reload the page again
3. Restart the Chromebook by holding down the power button for about 5 seconds, then start the Chromebook (alternative method: close Chromebook screen, then reopen)
Failing the above steps, open a Helpdesk ticket (https://cersd.mojohelpdesk.com/login/create_request#/ticket-form/17881) for assistance