When others can't hear you, first check the in-meeting mic button isn't muted (a red line means muted). Then open Settings → Audio and pick the correct input device — laptops often default to the wrong one when a headset is plugged in.
If the right device is selected and the input meter still doesn't move when you speak, your operating system may be blocking microphone access. On Windows, enable mic access under Privacy settings; on macOS, allow Orbit under System Settings → Privacy & Security → Microphone, then restart Orbit.