Hi @orangejuizze
Hope you’re having a great day ??
Well, I believe the issue is more related to the booking plugin you’re using. It seems that the calendar shortcode is developed to work only when the outer HTML container is visible on page load which doesn’t happen with Premium Modal Box widget.
Since this is not related directly to Premium Addons, then our devs would be glad to help you with that, so please send a message on our website from here.
Regards