Issues getting access to Chromebooks for a single user

Problem

The affected user gets a black screen when they try to sign in to Chromebooks only, it will work fine when they access to different device (Non ChromeOS). Or affected signle user has sync issues with bookmarks, history, etc.

Environment

ChromeOS. 

Solution

1-From a Windows or any other computer that lets the affected user sign in, go to https://chrome.google.com/sync
2-Once there, click the “Clear data” button. 
3-Try to sign in to a Chromebook again. 

Cause

Possible corrupted extension.