There could be multiple reasons why you are experiencing sound issues with streams on Discord. If you have enabled the Mute or Deafen feature in Discord, you won’t be able to hear Discord streams.

Discord is a chat app that’s similar to programs ... Right-clicking names includes the ability to deafen users so they can’t hear anything from other users or banning them from a server ...

It is all too easy to mute or deafen yourself so you can't hear other people or they can't hear you. Look to the lower left of the main Discord page where you can see your username and profile ...