Btw - they've changed everything since we last went through this.
The conventional wisdom on the WDW board is something like this:
1) Force close the app. (Doesn't hurt to clear the app cache if you can.)
2) Open a browser to time.gov
3) Open the app at 6:58am and have the Join Boarding Group button visible on the home screen.
4) Keep your eye on time.gov, and switch back to the app immediately before 7am.
5) At 6:59:59, hit the Join Boarding Group button.
6) Hit the Join buttons on the next three pages as fast you can. Don't even look at whether the right tickets are selected * - just go as fast as you can.
* The WDW app automatically selects the people who have valid park reservations that day - hopefully, the DL app will do the same thing.
I tested this out this morning in the DL app, and I would've gotten one had I had a valid Park Reservation. (The "success" screen for a test is basically "hey, you don't have a park reservation".)
The problem with the virtual queue page itself is that it seems to still be hit-and-miss - sometimes, pulling down to refresh works, sometimes it doesn't. (I think we had those problems in those first couple of months.)
EDIT: I blanked on which page was which. I don't think it makes a difference if you do it from the Home Screen or the Virtual Queues page itself - it's the Join Boarding Group page that's the problem. (I think most folks do it from the Home Screen.) Just don't hit Join Boarding Group until 6:59:59.