There can be many reasons for this, but the first thing to check is the status in your iceCUBED account.   

If the withdrawal status is "Pending" then the transaction is most likely being placed in the administration queue for approval (these are done a minimum of 3-5 times per day, Monday to Friday).  

If however the status on your iceCUBED account is complete and 24 hours have passed since making the request you will need to log a ticket with the service desk providing the TXR number for this request.   

Due to the service level agreement imposed on us by our hot wallet provider, we are not able to investigate withdrawals within 24 hours of the request.