Copying a field simply duplicates the field properties. You will need to go into each report and add your duplicate field in each report. But it does beg the question, why do you need two of the same field on the same report?
Was your goal to simply show your checkbox field in another area of a form? Is the original checkbox field a formula or one a user fills in? What about the duplicate? If you can provide more details, perhaps there is an alternate solution.
If you were simply trying to show the original checkbox field in another part of the form, you could just mirror the field (formula field that just references the original field). Then you don't need to worry about having that duplicate field on any report.
I played around with it some more and it's now working as I had hoped, although I'm honestly not sure what I did that fixed it!
