error 404 0n login submission

My login page appears well, but after filling it with my user details and clicked submit button, it will redirect to /wp-login.php which I have disabled using theme my login, thereby generating error 404.

I tried password reset, it still have the same problem. But the widget works well, as expected.

Please what should I do?

You can havea look at my site login page. Try to login with anything, it does not matter if it is correct details or not.

https://wordpress.org/plugins/theme-my-login/