I've been tasked to modify a program at one of our sites. Today I connected to the SLC 5/03, uploaded the program to the laptop and went online. I verified the key was in the middle position, but I can't perform online editing. Nothing happens when I double click the line I want to edit, the edit rung shortcut is grayed out, and when I right click on the rung to start rung edits, none of those options are available. I was able to go offline, complete the necessary edits and then download them to the PLC, but why can't I do this with online editing?