Xbox one live - Haven't heard anyone on the mic for years.

I would check your in-game settings. Often games will be set to assume you don't want to hear random game chatter. If that doesn't help try your chat mixer, Settings>Display &
Sound>Volume. Hope this helps.

Hi,

There's nothing to fix. You don't hear anyone talking because, for the most part, people aren't talking, well, not publicly anyway.

Ever since Xbox allowed party chat, most people like to talk in their own groups with people they know personally. I haven't talked in public game lobbies for years - a personal preference, and I'm sure I'm not the only one.

Hi, sorry are having issues. That's very odd that you can't hear someone even when you can see they are talking. It might be worth jumping into a party chat with someone to test it out and see if that does work. He is a troubleshooter that might be
worth working through also Troubleshoot Live Chat

Sorry to hear it. It may be that people are speaking to each other in their own party and that is showing the mics on your screen.

You could try powercycling the console by holding the power button on it for 10 seconds till it shuts down to see if that helps with your sound.

You'll have to enable chat output to be both headset and speakers. To do so, go to Settings -> Display and Sound -> Volume. In the Party Chat Output select the option of Headset and Speakers.