Hello Basile and sorry you are having problems with the contact form. The issue has been reported and will hopefull be fixed soon.
In the meantime I have removed the registration for you so please see if that helps.
(I work for Moodle HQ and usually respond to the contact form.)
If that doesn't work then the screenshot below shows the settings to report your site registration issue so we can discuss it privately.
- I need support with an existing product.
- Community sites.
- Registering my site.
