Plugin caused website error

I liked the demo and installed the plugin, but when I clicked to activate I got an error page. Now I can’t get back to the site to do anything. I decided to delete the plugin with File Zilla but that didn’t work. I don’t think it’s a server problem, but put in a ticket to the webserver but haven’t heard anything from them yet.

I’ve never had this happen with a plugin before. What can I do to troubleshoot this problem?

https://ww.wp.xz.cn/plugins/rsvpmaker-volunteer-roles/