Folder context in nautilus default (list with columns) view cannot be accessed when scroll bar is present.
Nautilus starts in a default view showing files in rows with detail columns (name, size, modified).
I use right-click to access a context menu. I typically use a context menu in a folder to create a new folder in the current folder or paste a file into the current folder.
If there are sufficient files (rows) in the folder that there is no white-space left in the bottom of the window, it is impossible to access the folder context menu. One work-around is to switch to icon mode.