warningFactur-X / ZUGFeRD containercontainerPDF
The filename declared in the XMP metadata must match an actual attachment.
The XMP metadata names an attachment filename that does not exist in the PDF.
Rename the attachment to the declared name, or correct DocumentFileName in the XMP. A receiver opens the file named in the metadata, so a mismatch makes the invoice look absent.
Nothing is stored, and the whole invoice is checked, not just this rule. A PDF only works if it is Factur-X / ZUGFeRD — a PDF with the invoice XML inside it.