The issue date (BT-2) is not a valid date.
UBL expects YYYY-MM-DD; CII expects YYYYMMDD with format="102".
The Billhorse validator checks XRechnung, ZUGFeRD and Factur-X right in your browser — your file is never uploaded.
Open the validator← All validation rules
Rule source: EN 16931 / XRechnung (KOSIT) or Billhorse check (BH-*).
