I've upgraded two laptops to Ubuntu 20.04 LTS. On one of them pressing Super (aka the Windows Logo key) opens the Activities overview. On the other one it doesn't, and I have to use Super+S, or Alt+F1.
The main difference between the laptops is that one uses Ubuntu on Wayland (where Super works fine), and the other one uses Ubuntu on Xorg (where Super doesn't work).
How do I make Super work on both laptops?
This is related to a recent Gnome issue. Currently using the Super key for the Activities overview works only on the first and fourth keyboard layouts, in Xorg sessions.
As a workaround until this gets fixed, you should set your primary layout as the first one.
Make sure sticky keys is disabled on the accesibility section in settings