Why saving apps on iOS doesn't work

Why is it that when I connect my iOS phone to my computer and press "Save project to Companion," the app downloads to my phone (it's saved in App Inventor), but when I launch it, I always get a black screen. It doesn't matter if the app just had a button with no code or was professionally built, the result is always the same. I have an iPhone 13 mini.

:red_question_mark: