Do not use the Clear Expired Blocks function in NukeSentinel™ admin. A bug has been found that can completely empty your htaccess file. Instead delete each expired block by way of the Blocked IP's List. This function does not use the same logic as the mass clearing does and therefore does not have this danger.Note:
Open admin/modules/sentinel.php in a text editor and replace the current case "ABClearExpired"; function with the one HERE. The logic has been recoded to prevent it from deleting the complete htaccess file.