I'm having the same problem. I found a fix on the WordPress site posted below, but don't know how to do this. Can anyone explain it step by step. I went to my cpanel, but could find nothing. Thanks
Sometimes the wp-login.php file may have been corrupted or uploaded incorrectly.
Delete wp-login.php off of your server and upload a new copy from a fresh WordPress download. Remember, overwriting file via FTP can lead to incomplete transfers.
Edit wp-login.php as follows:
Go to the case retrievepassword section, found under this comment:
// redefining user_login ensures we return the right case in the email
$user_login = $user_data["user_login"];
$user_login = $user_data->user_login;