Since you are working on a browser-based application so I advise you to use HTML mode for spy element and AA/Win32/Region Mode used for Windows Application. As I see it there are two ways to resolve your problem
1- First Spy password textbox via HTML mode in application modular & later use write stage to provide value to textbox
2- In case the Write stage will not work then you would move to GSK/GSKE text input methods and use the navigate stage.