On a multi-battery mission yesterday, the app was a little buggy.
On first battery, the drone returned to home without issue. I replaced the battery, started the drone and manually flew to mission altitude. Started DD and it detected the drone and a pop-up opened asking did I want to resume. I clicked Yes and the dialog went away and the telemetry screen loaded on the left like normal but the drone just hovered in place. I shut down DD and repeated with the same results as the first time.
I closed DD again, restarted it, ignored the notification and just went to the mission in my list and started it as if I was starting from the beginning. The mission loaded and the drone started at the abandonment point of the 1st battery.
So, it ended up working but not the way it was supposed to.
P4P on ios using DD 184.108.40.206