getting the no draw cursor when trying to use rectangle tool

I am doing assignment 9 (Perspective) in the Adobe Illustrator Classroom in a Book. After setting up the grid as it says, it tells you to choose the rectangle tool and then a grid side from the Plane switching widget, then draw a rectangle. When trying this my cursor changes into the pen with the line thru the circle, not letting me draw. Does anyone have a suggestion for why this is happening? I should be able to hover over the origin of the perspective grid and the cursor should turn to an arrow pointing left indicating that I can draw.

Thanks in advance,

Eryn