What is the reason I can't install Unreal Engine? HELP!

I downloaded installer in Epic Game website and I installed Epic Games Launcher.

But EVERYTIME when I tried installing Unreal Engine, this message popped up. And Everytime when this has happened, it seems Epic Games Launcher has got frozen that I can’t turn it off.

I want to install Unreal Engine. What is wrong with my computer? Please help me Thanks.