fatalPeppol BIS Billing 3.0profileUBLBG-6
The group "SELLER CONTACT" (BG-6) shall be provided.
XRechnung requires the seller contact group (BG-6); it is missing.
Add BG-6 with all three of: contact point BT-41 (a name or department), telephone BT-42 and e-mail BT-43. UBL: AccountingSupplierParty/Party/cac:Contact with cbc:Name, cbc:Telephone and cbc:ElectronicMail. All three are mandatory in Germany even though EN 16931 makes them optional.
UBL — context (/ubl-invoice:Invoice/cac:AccountingSupplierParty | /ubl-creditnote:CreditNote/cac:AccountingSupplierParty)[$supplierCountryIsDE and $customerCountryIsDE]
cac:Party/cac:Contact
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.