Both FIreFox and Chromium
it is like your install wrapper is not working or something,

even I went to this sight
https://helpx.adobe.com/flash-player.html


it still shows flash not working -- shows a number of directorys it searches and none of them are alive on Voild here you have your plugin installed onto your/this Void system. along with it does not match what it is looking for which is libpepflashplayer.so  not libfreshwrapper-pepperflash.so -- I even install chromium and still it does not have needed plugin libpepflashplayer.so -- I downloads Adobies libflashplayer.so  cp it into respecptive directories maknig a few of them that the sight showed in search path still no go in working