Nothing happens when pressing the hotkeys
It could be that Zwift is running in administrator mode (elevated) – it does that after an update.
How did that happen? When Zwift updates it elevates Zwift Launcher which in turn – when it starts Zwift – makes Zwift run elevated.
It is a simple thing to fix: Find the Zwift icon in the system tray in the Windows taskbar, right click it, and choose Exit. Next time you launch Zwift it will run in normal mode again.
Remember to run Zwift in window mode, otherwise some of the hotkeys will fail.