Mass action plugin is not firing automatically

-- HikaShop version -- : 2.6.4
-- Joomla version -- : 3.6.5
-- PHP version -- : 5.6.24
-- Browser(s) name and version -- : Chrome

I have created two mass actions, whose events are 'after user is created' & 'after user is updated'. But it is not firing automatically when user is created or updated. It is working fine when we click on process. I just want to fire these actions when events occurs. Is it possible, If yes, how?