My personal application created with xcode swiftUI disappears from my iphone, after 3 days message application not available. What is this development system for?
My app Xcode SwiftUI
You have probably a free developer license ?
If so, you have to rebuild app regularly (I thought it was every week, but may be shorter).
The point is that free licence is done to let you learn to develop, not really to build apps to use.