Manage your subscriptions link only works if logged in

This is an ongoing issue that I’ve never been able to fix. When logged in, I can click on the Manage Your Subscriptions link below the comment box, and it takes me to the appropriate page. But my site visitors don’t log in, and when they click on the same link it goes to a 404 error page, with this url showing at the top: https://www.ultimatepapermache.com/%5Bmanager_link%5D

Is there a setting in the plugin that causes this?

The page I need help with: [log in to see the link]