I can't hear or see specific people, but I can see others in the room

If the people you can't hear or see are within your view (aka you can see their chat head but not their video stream), they prob have their camera off. Just ask them to turn the camera on in the chat. If that doesn't fix the issue, make sure you have a strong internet connection wherever you are and reload the tab.

People get quieter when they're farther away, so you may need to move closer to see them. If they're not in your view, look for Wayfinders like the one below around the edges of your screen. Clicking one of these will move you closer to them.

If they're close to you but you still can't hear them, ask them to check their mic permissions (see below) and refresh the tab.