Proof of civil status document rejected.

I received a letter from l'Assurance Maladie. They asked me to submit "une copie de votre acte de naissance en langue originale" via postal mail with their original mail attached. I went to the Embassy of the country I was born and got the document and notarized by the embassy. I sent the requested document via postal mail about 10 days ago, but I received an email notification (final reminder) that my document is incomplete (proof of civil status is still rejected status). Where should I contact to understand what is missing?