[Plugin: Now Reading Reloaded] Errors with Admin Pages

When I try to manage books and click the save button, I am taken to https://blog.julie-h.com/wp-content/plugins/now-reading-reloaded/admin/edit.php which displays as an error 404 page.

When I try to change options, and click save, it takes me to https://blog.julie-h.com/wp-content/plugins/now-reading-reloaded/admin/options.php which is also an error 404 page.

When I add a book via ISBN, it will search for the book, when I click Use This Result, I get the same 404 error page, https://blog.julie-h.com/wp-content/plugins/now-reading-reloaded/admin/add.php

Any help would be greatly appreciated.