robot cant detect objects when machine is locked

I am trying to develop a simple wizard where I run a program at the start, typing username and pw and clicking enter, then running a script. When I am on the robot machine and the trigger time has come , that task starts and ends successfully however when I am out of the machine (signed out of the machine), the trigger gets started but the robot seems like that he cant find the window where to insert uname and pw, he runs the program and stops .. I need help with this issue asap ..