Sometimes Validate function does not return anything

[mfaisalsub]

I have set everything accordingly like success, fail, cancel, ipn function.
In my few transaction I am not getting validate true. Even in my IPN function did not get validate true. But transaction was successful. I have to confirmed payment status manually from SSL Commerz Merchant Admin Panel.

Basically, I am confused because some transaction is successful and some are not.
Can you tell me approximately how much time SSLCommez take to make a transaction successful?
Is there anything that I have missed?