Hey Fewzi,
Thank you for reaching out to us! I’m very sorry about this issue you are experiencing, let me help you to solve it!
I’ve accessed your page and verified that the problem is associated with your preloader, not with the calendar itself:
Using Chrome Dev Tools I’ve temporarily changed your preloader background color (#WPAjaxLoader, #loading-layer): As you can see, the calendar is already loaded / working as expected behind this layer.
I would suggest you to temporarily disable your preloader and check if the problem is solved after that.
Best Regards,
Patricia