00107: Signing certificate not valid
What it means
SdI code 00107 means the certificate used to sign the file is not valid.
The usual cause
The certificate failed SdI's validity check. The list of checks also counts a suspended certificate as not valid.
How to fix it
Check the certificate's status with its certification authority, sign the file again with a valid one and send it under a new name.
The code as published
Read the official document . Source: Elenco dei controlli effettuati sul file fattura del Sistema di Interscambio, version 2.0, published by Agenzia delle Entrate, fatturapa.gov.it, read on 8 November 2026.
Klarbon explains each code in its own words; the official wording is in the document linked above.