Why can't I pick 'built in audio' in audio outputs on Mac?

Hi everyone, Does anyone know why in cubase 11, using my MacBook Pro OSx Big Sur I can’t select ‘Built in Audio’ in audio connections output. Its been chosen in the device set up. Microphone has been allowed. Been getting this problem a lot, working on a project, then the next day, there’s no audio, and the output changes and I can’t change back to built in audio.