UMG button not automatically active on loading the interface

I have the problem when going out of the game level at runtime returning to the menu screen, the UMG buttons are inactive (not reacting to mouse over, mouse click) until I click anywhere in the screen, only then the buttons are active. For that, I would like some technical advise how to overcome this issue. My thinking is, it’s as if the screen needs to be refreshed somehow?

do you have something like this setup where you use the Set Input Mode Game & UI for example, it sets focus to the UMG Widget.

Set “Enable Click Events” and “Show mouse cursor” to true.

No, I didn’t. I was loading without that, but see now the problem. I was hoping the menu screen implementation itself would be sufficient, but obviously that’s not the case.
Thanks ayretek and Kauppaneuvos for explaining.
much appreciated

Thank you very much