I've been having the same issue for about three weeks with My Trips not showing up and the page asking me for a confirmation #, etc. Just talked to Delta app support, who first told me to "clear my cache and try a different browser." When I told him for the third time I was using the APP, not the website, he put me on hold for 10 minutes, came back and said he reported the info to his supervisors. They're apparently aware of an "issue" (and this only applies to Androids, of course, because doesn't it always?) and are "working on it."
I asked if there was a timetable for a resolution and he said, "We'll send you an update."
Right. Cool. OK.
So I guess it's paper boarding passes for me for the near future.