Hold ‘fn’ key while starting the app to reset back to clean state

If the app gets into weird state and not letting you login, try this:- Quit the app completely including the little QuickBooks icon sitting in the menu bar at the top, then press and hold the ‘fn’ (function) key and restart the app. It will prompt you to reset the app, click ‘Reset’ button to continue. The app will reset and quit. Now try launching it again and login.

dronelover about QuickBooks, v2.4.4