Paypal DoDirectPayment API is not sending the noti

Question

I am using the DoDirectPayment and DoCapture paypal API(s) to authorize and capture the Credit Card Payments via Paypal. But the Problem is that I am not getting any notification in Sandbox when the payment is authorized and captured. I get the Notifications only when the PaymentAction = 'Sale' but the notifications are not coming when PaymentAction = 'Authorization'.