Yep like others discovered my Multi-media keys weren’t working with my Microsoft Keyboard.
Saw this issue mentioned in manjaro forums. And the solution was to install xf86-input-libinput.
Which isn’t installed by default. Might be good to include it in the distro solving another issues from get-go.
Just a thought. As had me scratching my head as the multimedia keys were working then at some point during this year stopped working.