Cubase has hijacked my sound

Hi, I am running Cubase AI on Windows 10 with a UR22 ad two monitor speakers. For the first few weeks everything ran smoothly but then suddenly I lost sound on my computer whenever I wasn’t using Cubase. When I turn on my computer, I don’t have sound, the speakers only work if I turn Cubase on. I can only get audio from other programs if I open up, for example, a YouTube video, when Cubase is asking which project I want to select. If I if headphones into my computer, then I can get audio through them before opening Cubase. Why ihas the audio through my UR22 only become available through Cubase?

Thank you