Today my friend get this problem:
I ask the FTP account, and I found that the problem is because plugin “limit-login-attempts”. Before, I think this alert because any someone or robot try to hack or bypass the login, but from the logs, it’s normal.
To solve it, just access the file manager from your Cpanel or using FTP, than access directory /wp-content/plugins/limit-login-attempts. Open file limit-login-attempts.php and find this code:
add_action('plugins_loaded', 'limit_login_setup', 99999);
just remove it, or make it “comment” with give two slash like this:
//add_action('plugins_loaded', 'limit_login_setup', 99999);
Sorry, just a simple post, I hope useful.