Hi Jo, I believe that message refers to you selecting Full File Replacement as your upload option when there has been no previous submission. So essentially GovConnect STP can't replace a previous submission that isn't there, if that makes sense.
If this is your first submission and you're not replacing a previous one, you need to select 'New'.
Thanks Rav, but I do not see an option to select new by itself so I select new pay run/full file replacement, Once I click on confirm I get a pop up window that requires me to select a payrun I am replacing. it will not let me submit without that