Note that the password generated is only good for the challenge that was used to generate it. If you mistype the password, or otherwise have to get a new challenge, you will need to contact GTAC with the new challenge information.
If the failsafe account is disabled on the console port, one-time failsafe will also be disabled. It is not possible to disable one-time failsafe separately from the configured failsafe account.
See also: How To Create a Failsafe Account
If the switch is running a version of EXOS below 16.2, this one-time failsafe login is not available. In order to recover a lost password, one of the methods in the article below will need to be used:
How to Recover an EXOS Switch and its Configuration Without the Password