CSS forms suddenly stopped working

Suddenly, even though the formats of the different forms are still visible and correct in the preview when at the CSS Styles builder, they are not properly formatted in the website.
For instance, the form number 3120 that appears here in the middle and at the end of the page: https://www.orientaeuro.eu/fr/orientation-professionnelle

This form has exactly the same styling as the 3010 that appears still correctly here: https://www.orientaeuro.eu/career-guidance

Strange thing: This is happening both in Firefox and in IE, but NOT in Chrome. In Chrome it’s correctly styled. Of course I need it fixed for all the browsers, but thought that this detail might help.

https://www.ads-software.com/plugins/mailchimp-for-wp/