Thank you for trying my game! If I may ask, what kind of input device were you using? The game has primarily been tested with mouse and gamepad, both of which should work fine. However, I had another report of being unable to turn the camera with a Macbook's touchpad. It's something I'll look into fixing.
When you're able to turn the camera there's a red button next to the grill which when pressed will make customers turn up after after 10 seconds. I admit I should taken the the time to make an ingame tutorial to explain everything better.