I'm testing the plugin but the effect doesn't appear on my post

If you have set the effect to appear, say, once every 3 days for your visitors, and then it appears for you once, then the effect will not appear for 3 more days.

You can click the "clear my history" button, and that will reset your cookie, and allow you to see the effect again.

Or, while testing the plugin, you can just set it to show "always" (leave the "every X days" field blank, or set to "0").