What fare class does the website say is requested when you hover or click the "?" next to "Upgrade requested"?
If it says "RN", then that means your upgrade request is for a Premium Plus seat (which isn't sold on EWR-MAD yet, as far as I know). If it says "PZ", then that's a request for business class, but I would guess that's a bug, since W or higher is still required for a GPU to upgrade to business on this route.