Hi @MattLeach, please try the following : Create a new, aggregated audio device (see this posting of how to do that. Though counterintuitive, let participate in that device only your built-in audio device. Then load a project, go to Edit > Device Setup and choose the aggregated device as ASIO driver. Is dound coming out properly then? If so, what is happening if you switch back to Built - in Audio?
P. S. : You are still on Dorico 3.5.10, but there is a free update to 3.5.12 available for you