Mobile boarding passes are not available if both of you are on the same reservation/confirmation or flying internationally. If you'd like, you can make individual reservations for each of you and then you can use mobile boarding passes. Of course that also means you have to check-in individually or purchase EBCI (or have automatic check-in via A-List, or purchase Business Select fares, or upgrade boarding position at the gate). Not ideal, but that's the scenario. Lots of complaints about being unable to use mobile boarding passes when more than one person is on a reservation.