It is supposed to accept the whole path, so it's odd that it is erroring out. But try just putting the name in the parameter: AFO WIP Weekly.xlsx
If that doesn't work, let me know.
Also, instead of Wait 15 seconds...try Wait for Window. Have the workbook open when you build this.
Find window: By title and/or class
Then press select window, hover over the workbook until you get a red box around the whole thing, and then Ctrl + Left Click to capture window info.
Wait for Window to: Open
Then have your attach function.
Good luck!