Power Steering gone - reservoir full, hoses and belt seem fine

Hi there, hoping to get some help with diagnosing a problem.

Parallel parking yesterday I heard a screeching sound (sounded a bit like a belt, but maybe metal) and then my power steering went out. I finished parking, let the car be, went back an hour or two later, started it up, seemed to have power steering for a few seconds, and it was gone again (and still is). Checked the reservoir today and it's full. Looked around the hose coming from the reservoir and it doesn't look like there's been a leak anywhere. Aux belt seems to be taught and moving fine.

Any thoughts on what I should check next?

Thanks!