Cannot Access Admin Panel

I am using the “Better WP Security” plug-in, I switched the Admin Access URL from /wp-admin to a simple /admin then it will auto-direct me to the Admin log-in authenication page.

It’s working for about a month. Right now, whenever I want to access the /admin or /wp-admin it says that the page isn’t found, the site gives me a 404.

I didn’t change any settings, so I’m pretty confused why this is happening to my site.

Whenever I go to the /admin — it gives this new link, /wp-login.php?mebx335i2n4nycx1j1eqr&redirect_to=/wp-admin/, but it leads me to a 404. What seems to be the problem? Yesterday it was just working fine.

I hope you could help me solve my problem.