Annoyingly, the game works, I have tried sooooooo many instructions to get it to work aaaand NOTHING.
Until I decided to try and trick the screen as I noticed that the mouse icon for the game show us up briefly when I navigate back and forth between windows (using ALT + TAB)... Whilst navigating back to the game screen, before anything point your mouse at the button you want to click (e.g. 'browse servers') then navigate back to the game screen (using ALT + TAB) and VERY QUICKLY click on the game screen button you want... then you can start using keyboard arrows and ENTR/ESC to navigate and select...
WHAT A JOURNEY!... this is too much... I think game developers need to review this issue/code/function.
I hope it works for you so we can get developers to look into this!