Ambassador, British Airways; FlyerTalk Posting Legend
Join Date: Apr 2012
Location: Leeds, UK
Programs: BA GGL/CCR, GfL, HH Diamond
Posts: 42,936
If this was booked direct on ba,com it would be very unusual that an e-ticket was not issued straight away. The fact that you can't print a e-ticket from MMB does not mean there isn't one.
Is there a ticket number showing in the booking on the app?