While working on one PowerApp, I observed that the code written in first screen “OnVisible” event is not executing which means OnVisible event is not firing. I found couple of workarounds for this issue.
Workaround 1: Add a welcome screen with a simple button which will navigate to your actual screen.
Workaround 2: If you don’t like the Idea of having a welcome screen, you can use this one. Place a timer control on the screen (make it invisible and sent to back) and write the code in “OnTimerEnd” event.
Properties for Timer Control
OnTimeEnd event
Hope it helps to solve this issue.
Phani Rajasekhar 