Hi Ajay,
I did some experimenting because I’ve been plagued by plugin conflicts this week. The config area shows up if I deactivate the All In One SEO Pack Plugin. As a work around, I set it up while All In One was deactivated to get the config I wanted, but it disappears again with activation of the All In One SEO pack.
As I went through and activated my plugins, I also found that the customization area disappears when WP-Polls is active.
Your plugin is now looking wonderful on my site with the added CSS another user shared, but I thought you might like to know what the cause of the issue was.