Hi Julien,
Thank you very much for getting in touch with us ??
Unfortunately, the page you shared above is not working. However, I have tried to place a test order on your website and found the issue you reported.
It seems to be happening due to a direct modification of the default WooCommerce checkout page using ShopLentor. That’s why the place order button is not working as expected.
Could you please create a custom checkout template following the steps shown in the doc below?
https://woolentor.com/doc/build-a-custom-checkout-page-template/
Hopefully, it will resolve the issue. If it doesn’t, please open a ticket on our support center. Our support team will help you with this.
Best regards,
Tarek Aziz