Doesn't work in zerif lite

Hi, I’ve used WPFront Scroll Top before in another site I created (http://hippiefamilyvalues.com), and it worked fabulously there. That site was built from a child theme of Twenty Twelve. But the site I’m working on now (http://hansonfilm.org/may2015wp/), which is a child theme of Zerif Lite (downloaded from ww.wp.xz.cn), does not seem to allow this plugin to work – event though I am using the very same settings for WPFront Scroll Top. The arrow autohides fine after 4 seconds, but then never comes back again, whether i scroll or wait 4 seconds or whatever. Can you tell if the issue is with the plugin or Zerif Lite?

Thank you

https://ww.wp.xz.cn/plugins/wpfront-scroll-top/