Plugin Not Working

Hey, sorry to bother you, but I’m not able to get your plugin working.

Here are the steps I have taken:
1. Download and install plugin.
2. Create a new post, insert an image from the media library, and publish.
3. Post appears without a featured image

I really want to use this plugin. Could you help me out? My website is http://www.thefinancialengineer.net

https://ww.wp.xz.cn/plugins/easy-add-thumbnail/