If you don't have access to the password - e.g. saved in your browser on your work computer - a fellow administrator will be able to reset it for you. If there is no-one available who can, contact your support provider. If you are contacting them by telephone you may be asked for a 4 digit pin from the organisation record, so you should make a note of this before you need it.
What if the code doesn't work?
Codes can only be used once and must be used within an hour (from the time they're generated). If you're confident that neither of these are the reason a code hasn't worked for you, please contact your usual support provider.