No sound when playing YouTube or Facebook?

Hello, Here are some ways to fix it : First, check if your tab is muted. To check, right click the tab and see if it is muted. If not, go to the next one. Next, check if your volume mixer is muted. To do so, open firefox and start playing a video, right click the speaker icon on windows taskbar, and select open volume mixer or (Open sound settings -> Volume mixer). Then, find if firefox is muted. If firefox is not muted, follow on. Lastly, go to Windows Settings > System > Sound, scroll down to Advanced sound options and click "App volume and device preferences", then find Firefox check if the output device is set to the device you want it to, rather than being set to "None" or a disconnected device.