A calm, ordered checklist for Belgian Odoo users when Peppol starts failing without a clear explanation.
If the XML is present and Odoo says sent, do not assume the document is the problem. Most Belgian failures start with identifiers, stale registrations, or access-point state.
Look for the exact symptom first: sent but not delivered, invalid signature, or partner not found.
Check the recipient as a full Peppol participant identifier, not just a company name.
For Belgian companies, compare the enterprise-number route under 0208 against any VAT-number route under 9925.
Bring the participant ID, the symptom text, and the last send attempt together before opening a support ticket.
That turns a vague support request into a provider-ready incident.
If Odoo marks an invoice as sent while the customer sees nothing, you are usually dealing with routing, registration, or access-point issues rather than broken invoice content.
Open issue pageThe revalidation prompt usually signals stale participant metadata or a registration mismatch. This page shows what to refresh before you resend.
Open issue pageAn invalid request signature is usually a provider credential or environment problem, especially after database copies or restores.
Open issue pageMulti-company setups, duplicates, and restored databases can leave Odoo pointing at the wrong Belgian participant even when the invoice itself looks fine.
Open issue pageGuides are useful when the pattern is familiar. When the latest failure still feels fuzzy, run the analyzer with the exact provider message or XML so you can separate routing, profile, and provider-state problems.