Trying to make the popup appear when

Hi,
I am trying to make a popup load when the user clicks on a link. For this purpose, I configured a new popup to use "Appear when user clicks on a CSS selector" and entered the class name ".wishlistupgrade". Then, created a link in my web page having that class name in the class attribute ..

However, it doesn't work.

I also tried to setup it using an ID in a similar way, but it doesn't work.

I checked the Settings and the popup loading method is using Page Footer.

Any ideas why this may not be working?

I also could see some related threads, but unfortunately without success:
-
https://premium.wpmudev.org/forums/topic/a-popup-to-appear-when-you-click-a-menu-item
- https://premium.wpmudev.org/forums/topic/ive-setup-the-popup-plugin-and-tried-to-make-it-work

Look forward for your comments,
Julian