If three consecutive failed administrator login attempts are made that IP address will be blocked for the amount of time specified in your security settings to prevent against dictionary password attacks. You can wait for the ban to expire at the time displayed on in the error message, login from a different IP address, or follow these instructions to lift the ban immediately:
- Login to your database administration interface (usually PHPMyAdmin via your server control panel)
- Select the WHMCS database in the left-hand menu
- Browse to the tblbannedips table
- Finally locate the row containing your IP address and click the corresponding red "X" icon.
The ban will now be lifted and access to your WHMCS installation restored. Should you find yourself getting banned often, consider adding your connection's IP address to the Setup > General Settings > Security tab > Whitelisted IPs list.