Z Class on AC is not "Youth Standby". It's a consolidator fare class. Since the beginning of this year, it's ineligible for mileage accumulation. That explains why your Mileage Plus number does not register in the booking. Paper tickets are issued by TravelCUTS because they control the booking and ticketing on these fares. If you needed to make changes, only TravelCUTS can do it. FWIW, TravelCUTS tickets have gone up so much in price since the AC/CP merger that sometimes you're better off buying an L Class ticket (published discount economy) and get your miles.