Just want to add a note here...
Most of you know that brute force block can be triggered from multiple incorrect login to cPanel, Horde Webmail, etc..
But do you know that if you use email client (e.g. Outlook, Mac Mail, etc.) to download emails and if your client has the wrong email password, it can also trigger the blocking as well? So if your email client tired to send/receive emails a couple time and indicated it doesn't have the correct ID/password, please check with the info FIRST before try again...
Else, you might have to wait for 15+ min again...