Appendix
A Verification failure reasons
The Reason shown on the Invalid tab of Verifications, and what it usually means.
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| Reason | When it happens | Usually means |
|---|---|---|
| Invalid product | The code or link is unknown, its product was deleted, or an NFC tag was not finished writing. | Fake or mistyped code |
| Invalid PICC | NTAG 424: the encrypted tag data does not decrypt to the expected tag. | Forged or cloned tag |
| Invalid CMAC | NTAG 424: the tag's cryptographic signature is wrong. | Tampered or copied link |
| Invalid signature | EM4425: the signed data is malformed or the signature is wrong. | Forged tag |
| Invalid UID | The tag's unique ID does not match the one registered for the product. | Swapped or forged tag |
| Invalid transaction | The link's transaction does not match the product's integrity record. | Manipulated link |
| Already verified | A secure tag's one-time code was used before: the same link was opened again. | Re-shared link or replay |
| Read counter mismatch | The tag's counter went backwards compared with earlier scans. | Cloned tag |
| Product is blocked | The product was blocked by your team or a workflow. | Stolen, recalled or suspect item |
| This authentication has been blocked | This particular tag or code was blocked. | Known copy of a tag |
| This product is only available for internal verification | The product line is restricted to internal checks. | Not for public scanning |
| Unspecified | An unexpected error during the check. | Contact support if frequent |
Reasons in failed page rules#
Failed page rules group the reasons, so one rule covers related failures:
| Rule condition | Reasons |
|---|---|
| Already scanned | Already verified |
| Blocked or withdrawn | Product is blocked · This authentication has been blocked |
| Internal use only | This product is only available for internal verification |
| Authentication failed | Every other reason in the table above |