I am having this same issue.
I’m using Nginx, and copy-pasted your example config included with the plugin, and also reinstalled memcached and the memcache extension using the instructions here. I can interact with memcached on the CLI, and php info shows that the memcache extension is loaded, the the WP-FFPC plugin shows that it’s down.
I’m happy to send you any files at all which can help diagnose the issue!
I am also not able to use the redirection plugin. It breaks all of my normal links in WordPress! Without it, I have no issues navigating my site, but with it on Nginx, I can only access the home page.
