[2022] UI just disappeared, couldn't find how to activate

While you are in a match, pause the game ("Esc" or "Start" on controller), and there should be a prompt at the bottom of the screen showing you how to re-enable it!

Additionally, if you are playing with more than 1 player locally, the cooldown bar will be hidden because there are more than 1 of you on the same screen and you'll have to rely solely on the icons above your healthbar.

Hope that helps!
Brett