I am new to Inkscape so this may be caused by a simple newbie error...When I use the square or circle tool, no squares or circles appear. I use the fill and stroke commands but to no avail.
Reading your article solved my problem. Going to the Object menu and opening the Fill and Stroke window enabled me to see that opacity had been set to 0%.
Thank you for your help! Now I can get back to learning Inkscape which I am enjoying.