Disqus plugin not working.

Hello,
I was discuq on one of my site for some time so I decided to use it on my other site too. I installed the plugin and activated it but it was showing nothing after I clicked on “Disqus” to get activation key.

After that, I also checked out my other site on which it was working on some time already. Although it was working properly on that other site but it also showed nothing when I clicked on plugin itself.

Note: Both sites are using latest Disqus version.
Please help as soon as possible.