The new QuikTrak machines appear to not be able to print out the open sleeper tickets - there was a thread a few months ago where someone struggled mightily to get their open sleeper ticket because their local station only had the new QuikTrak machines which wouldn't let them print out the open sleeper ticket.or QuikTrak machine
They may still offer the mail option, but that's only an option when the booking is at least 10-15 days in advance (I forget what the exact cutoff is/was.) Otherwise you're stuck with having to get it from an agent at a staffed station or try to find one of the remaining older QuikTrak machines.