I've just updated my system to Ubuntu 20.04. I'm facing issues with missing icons and alignment of icons in the top bar. I've attached screenshots below.
Try resetting the icons to the standard icon theme (eg. Yaru).
Had the same issue. I was using a non-standard icon theme called "paper" that is not available for focal.
Changing to a preinstalled icon theme using "Tweak Tools" solved both problems for me. "appearance" tab in Tweak Tools where one can change the icon theme