Les modifications dans les formulaires ne sont pas prisent en compte lors de la reception du formulaire. pourquoi?

What changes? Are you referring to changes not being saved?

Maybe style changes in the Designer feature?

Perhaps conditional changes:

Please do provide us more details to find out a solution for the issue, in the mean time, I would recommend you to:

1) Try clearing your browser's cache.

2) If option one does not work, please try applying the changes in another browser, we recommend using Google Chrome ore FireFox.

In addition to this, clearing form's cache may help: http://www.jotform.com/help/229-How-to-Clear-your-Form-Cache