form send but no email is sent

Hi!

We’ve noticed an issue with our forms from 2 websites;
https://remise-en-forme.be/contact/
https://krav-maga-mons.be/contact

When a request is made, it says it’s sending correctly but no e-mail is sent afterwards and so the request is lost (apart from Flamingo)
On both those website, we have the Sidney Theme and we’re using Site origin builder and elementor.

Do you have any idea on how to fix this?

Thank you!
Laetitia

The page I need help with: [log in to see the link]