You’re encountering a common problem with free plugins. They aren’t always up to professional standards and sometimes the developer is inclined to lose interest and disappear.
I am in the process of replacing Air Date/Time picker throughout my app. Even though no known change has been made to the plugin, two or three weeks ago it began sporadically producing empty results (value) even when the user picks a date.

This is the kind of behavior that changes “free” to expensive. Very expensive.

Best of success in your Bubble experience.