When upgrading to AEM 6.2 from previous AEM version, the admin user can sign in to CRXDE, but the screen is blank. The user is unable to view the node structure.
This is because of the nosamplecontent runmode which applies the production ready configuration. This runmode disables CRXDE functionality for increased security.
There are some ACS Commons tools that could help in exporting users from AEM in order to perform a diff: