File upload in CMS fails

[Axel Leroy]

Hello,

I set up a fresh install of Open edX and My colleague set up its first course which needs to upload a file for him to review.
But every time a student tries to upload its result, it is greeted with the following message :

L'image n'a pu être chargée
Une erreur s'est produite lors de la récupération de l'URL de chargement.

(The picture could not be uploaded. An error happened while fetching the upload URL)

The request and response made by CMS are attached to this post.

Do you have any idea of what could cause this ?

Thanks