Usually a user who has difficulty signing in due to a problem with VAN access can simply be resent the authentication code. That's not always the case, though, especially when the 2 factor authentication proves to be difficult. In these cases, admins must click "reset all" next to the 2 factor authentication methods section in the User's profile. This will then allow them to resend the activation link. If this still doesn't work, especially if the user has a previous account with a different 2 factor type that stubbornly refuses to go away, VAN support will need to be called in.