Hi @naisim,
Sorry to hear of the problem you are having.
Could you please share me the exact error message that you are getting by copy pasting it here or sharing the screenshot of it?
For screenshots, you can simply provide a link to an image through Google Drive, Dropbox, screencast.com, http://imgur.com/ or other image service. 🙂
The WordPress PopUp plugin is working fine on my site.
This can also be due to plugin/theme conflict on your site.
To find find out plugin/theme conflict you can just try on your development site using default WordPress theme like Twenty Thirteen and deactivating all other plugins as displayed in the following flowchart to know which theme/plugin is conflicting if any.
http://premium.wpmudev.org/wp-content/uploads/2013/12/Support-Process-Support-Process.png
Kind Regards,
Vinod Dalvi
