Comments not getting posted error 404 Not Found

Hi,

Comments are not getting posted on my wordpress site (http://www.trendydaddy.com/).

When I post comment, it gives error 404 Not Found and url becomes like this http://www.trendydaddy.com/wp-comments-post.php

I have tried
1. disabling all plugins
2. access is already 644 to wp-comments-post.php
3. uploaded a fresh “wp-comments-post.php” file
4. changed custom permalinks back to default and then back to custom structure
5. removed / from the end of permalinks
6. repaired the database using WP-DBManager plugin

nothing worked 🙁
kindly help

https://wordpress.org/plugins/comments/