HTML5 mobile problem

Hi! I have compiled a small sample project in HTML5. The game works fine on Windows, but on mobile I can’t focus the game. I have added window.focus() in a script inside mygame.html, I have tried other methods but none works. Apparently without this focus issue, the game runs almost perfectly with all the added animations.

Why on mobile do you lose the focus of the game? Using Unreal engine 4.21.2