I got that error when I tried using mismatching VBOs to ineract with the excel file. We have 3 separate VBOs for interacting with excel and sometimes they dont play nice with each other. Double check that you are using the same business object to open an instance of exce land the nopen the workbook.
Just in case you're very new to Blue Prism, I have attached an example of how to open an excel including the action inputs and outputs. Putting it there just in case someone else searches for how to do this on the forum in the future and finds this thread. Though it might be of use to you as well.
If the problem is something else, was this something you had difficulty with in older versions of BP as well?
Kind regards,
Ben