querySelectorAll does not work for element

I am having trouble trying to select the child nodes of an element having the specified div class.

In the debug window, I have checked that the variable element is indeed Element type. The line docContentRef.current.querySelectorAll shows there are existing elements with the practice-note class.

Now when I retrieved the element having child nodes with the practice-note class and using the line element.querySelectorAll, it does not return the expected list of 4 items.