A withdrawal may fail if the receiving bank is unavailable at the point the withdrawal is initiated. This is usually preceded by an elongated processing period. 
When withdrawal fails, the funds are usually locked from the user and on intervention by our dispense error team, it could be retried or rejected, with the funds returned back to you for retrial.

Also, your withdrawal may fail if you’re trying to withdraw all the funds in your wallet without leaving enough balance for the withdrawal charge. You can learn more about the withdrawal charges here

Another reason a withdrawal may fail is due to a downtime by one of the other counter-parties involved in the process, such as our payment partner  or NIBSS being unable to validate the transaction or the destination account number during the withdrawal process. Not to worry, our dispense error team tracks every failed withdrawal and attempts to get swift resolution of all unique cases of this.

If this lingers for long please create a dispute via the trade page.