You could have requested the payout higher than the balance available, or you have sold shares or made profits, that can be withdrawn only after T+2 days in case of Equities or T+1 day in case Derivatives (FNO/CDS/MCX) respectively.
Note – If you are trading in both equity and commodity segment, and if you have a negative balance in either of the accounts, your withdrawal request will be rejected. You will have to clear your dues to make a withdrawal.