WhatsApp notifications MUST be allowed!  Please check: Your phone settings -> Apps -> WhatsApp -> Notifications – ON

WA Auto Reply cannot reply when WhatsApp working in the foreground, for example in time you are sending messages. Do not leave WhatsApp on the home screen (in the foreground)

WA Auto Reply cannot reply to Individual or Group if you check to stop notifications from being shown in your notification bar. To check, Tap and hold the individual or group chat in the Chats screen. Then Tap the Mute icon in the top right corner. Check Show Notifications checkbox .