My documents are rejected without reason and I cannot access the help line

Hello,

I'm trying to get a certificate through https://etudiant-etranger.ameli.fr/espace/#/student-area, but my documents for "Proof of registration for the current academic year" and "A certificate of income" get rejected with a reason "Invalid document", even though they are official documents. The former is even directly from my education institution. I'm trying to call the help line (00 33 811 36 36 46), but all I get is an automated response which ends with "thank you for calling" and then the call ends. I'm calling on a Thursday (August 15th) at 11 AM. Maybe it's closed because of a holiday?

What should I do? I don't know what's wrong with my documents, and my phone calls to the help line are not answered.

Thank you very much for any help!