The window is invisible and thus cannot be activated

Without some greater details of the specifics of the component, all I can offer is a guess.



My guess is that the Alias/Mapping of those password fields may not necessarily be the same component visible on screen and so the keyword test attempt to interact with them may be getting misdirected.  I'd suggest using the Object Spy and see what you can find out about those components and make sure that there's not two layers there of some sort that is causing something like this.