Can't submit August STP files

I have uploaded my STP files to the portal, but when I go to submit them, I run into a problem.

It asks me which payrun I want to replace and lists all my files from last month. I don’t want to replace any of these.

When I submitted files in July, it always showed me the current file to over-write, which while it sounded a stupid thing to do, worked out fine. The file I submitted over-wrote the file I was submitting.

But now, the only files available to over-write are last month’s files.

What is going on here, and how do I submit my August payroll files? It won’t allow me to not select any file.