Assignment 2: System exception. Retry: 1. The selector is not valid at Source: On Element Appear Correct Next Page1

Is your month selector not dynamic for each month?
You are doing the process for each month and the click should be something like this:

"<html title='ACME System 1 - Reports - Download Monthly Report' /><webctrl aaname='"+item.ToString+"' parentid='searchForm' tag='A' />"

For this you can edit your selector to add new attribute aaname and then make it dynamic.

Yes the Performer performance issue.
Seems something common when doing this assignment.
Small tweaks if you have not already done it in the thread below: