Hi sudharshini,
A "Not connected" error occurs when the object used to interact with the external application is not attached to it.
Typically whenever the application is launched it gets attached to the Object by itself. But due to some reason (depending on what you are doing in the diagram) it gets disconnected and is not attached/connected and it needs to be explicitly attached using the Navigate (Attach action) by making use of the suitable parameters like Window Title, Process Name etc.
Another thing to keep in mind is if an application is already connected to an object then attaching it once again using the above approach will fail. So a good practice is to check whether it is already connected or not using the IsConnected action. In the Reader stage select the Root (topmost) element on the left hand side and in the dropdown choose IsConnected. Check the resulting data item using a Decision stage to see whether it is returning a True (Connected) or a False (Not connected).
