Why is there no audio in my recording?

No audio in a recording almost always comes down to an audio source not being switched on before you started, most often the microphone toggle being off or the tab or system audio not being shared.

Work through the likely causes in order. First, the microphone narration toggle: if it was off (or muted) you will get a silent voice track, so re-check the mic toggle and pick the right input before recording. Second, the captured audio source depends on the mode: tab recording captures that tab's audio, while desktop recording captures system audio through the Web Audio API, so make sure you chose the mode that matches the sound you wanted. Third, Chrome permissions: the browser must be allowed to use the microphone and to share the screen or tab, so grant the Chrome screen-share and microphone prompts when they appear.