I'm having the same issue. I use a Microsoft Wireless Keyboard 800 Model 1455. Volume controls - i.e. Vol Up, Vol Down, Mute - all work, but play/pause must be used out of the FM window. The same applies for the calculator (why someone would want to use it, I don't know...). This is on Windows 10 Pro Version 1703. This is constant in both the windowed and full screen modes.