I’m running into the same issue after upgrading to 5.1. My widget component window is set not to receive focus.
I found this on Unreal Slackers Discord
c++: FSlateApplication::Get().SetAllUserFocusToGameViewport();
blueprint: Set Focus to Game Viewport | Unreal Engine Documentation
My code to click is:
const FKey LeftMouseButtonKey = FKey(EKeys::LeftMouseButton);
PressPointerKey(LeftMouseButtonKey);
ReleasePointerKey(LeftMouseButtonKey);
FSlateApplication::Get().SetAllUserFocusToGameViewport();
and it seems to work as before now.