Hello PeiYouLiao,

Regarding your issue, it seems like you've created your own theme in your EasySocial and when I try to view source of the group post page, the EasySocial css file that loaded from your theme is empty.

http://yoursite.com/components/com_easysocial/themes/jf_connecto_es/styles/style.min.css

If I change your EasySocial theme to use the default 'wireframe', then the group header is showing correct on your blog post. Please see http://screencast.com/t/Enmo3nTatu

Hope this help and have a nice day!