We always recommend using a high priority fee when you sell your Bitcoin to avoid long wait times.
Currently, the recommended transaction fee is: 18 satoshis/byte (or 0.00018 bitcoins/kilobyte).
In most cases, the higher fee you set, the quicker your transaction gets completed and the less time you'll have to wait at the machine.
You are sent a redemtion code to cash out your Bitcoin sale after your transaction receives 1 confirmation on the blockchain. If you set a low miner's fee when you send us your Bitcoin, it will affect how quickly your transaction will receive this confirmation. Your Bitcoin transaction could be ignored for an unknown amount of time until a miner decides to process it and solves the block; this could be several hours to several weeks and, in some cases, never. Make sure to use a wallet application that allows you to set a transaction fee or transaction priority and, at a minimum, set your transaction fee to Normal priority.