Hope you have specified the index starting with 0. I have got this error before when i tried to pass an index of a page that wasn’t there.
For e.g - if the workbook as 4 sheets and you try to pass an index other than 0-3, it will give this error.
Thanks for help, but this is not the case.
As I said, the same work flow works in some occasion - especially when started in debug mode. As I am using copy workbook activity, in most of the cases it crashes there. It seems that excel needs more time then Bot.