Zoom events registrations : users can't register

Hello. We launched our event registrations on tuesday, and it appears that some of our interested prospects can't register. They live in safe countries like Martinique (part of France) and Luxembourg. The registration button for them appear in grey, they can't click. 

We were not aware of those restrictions before subscribing to Zoom Events. What can we do to make them able to attend our event ?

Thanks in advance.