thank you - this worked like a charm on my M2 
Honestly, it’s absolutely wild that for a “bug” which has been acknowledged back in 2021, Steinberg hasn’t been able to come up with a solution in 2024.
Perhaps I’m wrong, but I’m under the impression there are many people who use DAWs on the go, plugging headphones in and out is a fact of life.
Aggregate devices are a patchwork solution, they don’t allow you to control volume at the system level if not using some obscure script from Github.
I just tried it and it works for me. The system output device should be the headphone out, not the aggregate. The aggregate is just for use by Cubase. Use the output level control in the menu bar to control the headphone level for both system audio and Cubase output.
Yup, this fixed it for me.
Same exact thing happened to me tonight on my Macbook Pro while on the Cubase 14 trial. Almost deleted the app until I saw dreikelvin’s post.
I had to unplug my Studio Display, change the audio connection, and then re-plug the Studio Display.
Not sure if you’ve heard of Loopback (Rogue Amoeba) and/or if your issue is also related to aggregate devices, but it’s a wonderful overall app/device rerouter/aggregation tool. I have 2 Studio Displays on either side of my XDR and will use Loopback devices in different ways to use them as monitors; either “dual surround” between both (which is more experimental) or moving L/R to each individual SD (all 8 channels) like below:
If you’re looking at C14 Pro, that will include Control Room which, if you build out an aggregate device with multiple audio destinations, will let you configure switchable Monitor selections on the fly. Not sure if any of that is relevant, but figured I’d post that.