Menu & Search Icons don’t show

Hi! I'm Arjan and I'm using the Zubin Pro theme and in the topright corner of the webpage I built there should be two icons for the menu (the three lines) and search (the looking glass), but they don't show and all I see is a square. The same goes for the 'move up' button that appears after scrolling down - that one is also just a square. Is this a known issue and can anyone help me in solving it? Thanks!