My Gmail pane was not populating. I normally resolve this by deleting the account in the Gmail sync plugins section in settings and then adding it again. When I try this with the new Windows desktop app, it successfully logs in but then leaves my Gmail inbox visible within the login dialog box, rather than closing after loading it and returning to the settings dialog like it usually does. ESC will close the dialog with the Gmail inbox and return to settings but the account is not actually added.