So when I updated to Ubuntu 17.04 I opted for GNOME flavor since we all know we'll be using it by 18.04 anyway. But oddly my superkey is no longer functional. It worked fine in 16.10 default Ubuntu, and works fine in Windows. If I check inputs under Region and Language and click the little keyboard icon, all of my keys seem to function fine except both super keys. Also the | key is in the wrong location, but at least it works. I am using English (US) which is what I've always used in the past, and I did try other layouts just to be sure, such as English (UK). Again, all the keys worked except super. I'm using a Logitech G710 gaming keyboard, but again, worked in 16.10 Unity. Any ideas?
Gnome Tweak Tool, and set "Icons on Desktop" to ON. Believe it or not, that will fix your super key.