Why this code doesn’t show number 0, but it works when the score increased…
GUI.Label( new Rect(Screen.width / 2 - loseWidth / 2 + losePosMargin / 4, Screen.height / 2 - loseHeight / 2 + (float)fontSize * 2 + 4, loseWidth - losePosMargin / 2, fontSize + 4), "Score: " + gameScore);
Since your
GUI.Label( new Rect(Screen.width / 2 - loseWidth / 2 + losePosMargin / 4, Screen.height / 2 - loseHeight / 2 + (float)fontSize * 2 + 4, loseWidth - losePosMargin / 2, fontSize + 4), "Score: " + gameScore.ToString());
is inside if(lose) condition, your Label for Game Score will be shown only after the game is lost.