There are some cases when cache plugins affect Popup Builder plugin's work, crashing your popups sometimes.
Autoptimize is one of those cache plugins. And to make your popup work with this plugin, follow the steps:
1) From your WP admin panel go to Settings -> Autoptimize
2) Inside the Autoptimize plugins section at the top, you will see 'Settings Show advanced settings' button, click on it
4) At the bottom of the same page, click on the 'Save Changes and Empty Cache'
5) Check the popup again.