Are you capturing OBS Studio's own audio with the plugin? If so, why? Furthermore, I wouldn't recommend it. If you are using it to capture alert sounds, e.g. Streamlabs or StreamElements, you need to use the Browser Source's "Control audio via OBS" setting. In fact, this is the correct way to capture any browser source audio output.
As for the Stream Deck side of things, I take you're talking about the Elgato software's interface? If so, what kind of sound is it emitting that you're wanting to capture?