Thanks to all for your help. I am still at it and still have had no luck. I did end up doing two factory resets. At least now I am not getting the message that Calibre does not know what firmware I am using. So that is a good thing. But still, the books are not showing up. Very aggravating.
When I try to send to the device, via Calibre, it wants to convert the book either to kepub. Epub, PDF or txt. I thought that I had read that the Kobo Aura HD will also read mobi. The books in my Calibre library are in the mobi format as that is what I have used for my Kindles. And in answer to your question meeera , I did try clicking "Attempt to support newer firmware", but alas, no luck.
GeoffR , the firmware that I now have is 2.8.1 (b2c05cda0e, 9/20/13). when I did the previous factory reset it was 2.5.1 something. You had also mentioned that “You can load books onto the Aura from Calibre via wifi, without plugging in to the USB port.” I am not computer literate at all and did a search in the forum of how to do this. I found a thread but am not able to figure out how to get the Kobo to see my Calibre. I think that I have Calibre set up correctly. If you know how to do this and could give 'Elementary' details, I would be most grateful.
davidfor I did check the KoboTouchExtended driver, it was the version prior to the 2.2.9, but I went ahead and uninstalled it anyway. It has not made a difference either-way.
So I have a beautiful Kobo Aura HD Espresso that I am not able to use!

I am certain that I will love it if only it will take my books!
Thanks again for everyone's input.