Clicking an element that is not currently visible in the viewport requires scrolling. Sometimes the element itself is inside a scrollable container. Other times a parent container must be scrolled first to bring the child container into view. A robust test must handle all these cases.
The button below is placed far down the page so it is out of the initial viewport.
The button is hidden inside a scrollable container. You need to scroll within the container to reach it.
The button is inside a nested scrollable structure. First scroll the outer container to reveal the inner one, then scroll the inner container to find the button.
↓ Scroll down in this outer container to find the inner box
The button below is hidden until you hover over its parent row — similar to action buttons in email clients that only appear on hover.