Cubase LE AI 7 getting no sound

Upon fixing a lot of problems involving a new computer and being unable to redownload Cubase, I immediately run into a problem I remember having when I first got it with my old computer. Upon creating a track at the start of a project, I am getting no audio at all, whether previewing a sound or putting in notes, whatever. No sound at all. I’m using the Halion Sonic SE instrument that comes with it and tried various sounds in it (Steel Guitar, Nylon Guitar, Grand Piano), but no sound at all. I’ve made sure the track isn’t muted, tried increasing the track volume, fiddled around with every setting I could think of or thought I remembered being part of the problem before, and nothing is working. How can I get audio to work on it?

As a bonus or side problem, having Cubase open seems to also cause problems with YouTube videos, as noticed when trying to find a solution on YouTube for the problem. Any possible fix for that?

Stop " fiddling around with every setting you could think of" and start following the steps outlined in the getting started manual. If necessary post, which steps don´t work for you. And while you´re at it, provide some info on your system.
And since you´re also not mentiong what problems it causes with youtube, try unschecking “Release ASIO driver when in background” in Device setup - VST Audio system.