The Chromeboxes display Digital Signage in kiosk mode. This means they only show the Digital Signage website and don't show the browser window.
To access the settings of the box, you may need to stop the kiosk mode.
1. Connect a keyboard and a mouse to the Chromebox via USB
2. Restart the Chromebox
3. While Digital Signage is loading, you will see this screen
4. As indicated on the screen, to stop the kiosk mode, select Ctrl + Alt + S
5. You will see a login screen. Log in to the Chromebox with any Google Account.
This has nothing to do with the MSSNGR login. Just use any (private) google account. (Please be aware that the keyboard might be set to another system or language as the keyboard settings might be surprinsing.)