Preview Button Only Works When Post Is Published

When I set up a popup, I’d like to be able to preview it. However, I’ve noticed it can only be previewed using the preview button when the popup post itself is published. If it is set as scheduled or draft, the preview does not work.

My popup is set as a timed popup without cookies on close, so it’s not a cookie issue. It’s the safe in different browsers. The preview works as expected when the popup is set as ‘published’ but fails when it is saved either as ‘scheduled’ or ‘draft’.

Is there a way to preview popups while the popup is saved as ‘scheduled’ or ‘draft’, without having to publish it first?