PO due date "Schedule due date is out of range"

Hello,

We are currently having an issue with the PO due date and I can't seem to find any answers. When we create a PO the due date must fall within 30 days of the PO date else we get the error in the title. I have had our developer go into the Application Designer to check if PO_LINE_SHIP.DUEDATE has the "Reasonable Date" checked and this was not the case, only "Required" is checked in the "Edits" tab.

Another item I checked was the closure calendar (prompted to do so by PeopleBooks) and as this isn't a feature we use I have also removed that from the possible causes.