When will I get the refund, if I did not get the IPO shares allotment?

If you did not get the allotment of the shares for the IPO you've applied for, then the bank will unblock the frozen amount from your bank account after receiving instructions from the IPO registrar. You will get funds back within few days after the allotment. If funds are not yet credited then raise a query to your bank to unblock the application money.