A DESCRIPTION OF THE PROBLEM :
Certigna is French commercial CA.
The ANSSI (French National Security Governmental Agency) recommend this CA. It is used on many governmental websites (eg elysee.fr, service-public.fr, ...) and for API endpoints.

This root CA is included in Microsoft Windows, Linux and Firefox trusted CA.

Informations about this CA can be found on https://www.certigna.com/autorites-de-certification/
  - Certification policy : https://politique.certigna.fr/en/PCcertignarootca.pdf
  - Certification practice statement : https://politique.certigna.fr/en/DPCcertignarootca.pdf
  - der file : https://autorite.certigna.fr/certignarootca.der
  - crl file : https://crl.certigna.fr/certignarootca.crl