Re my previous post:
I tried something different this time:
I returned my ebooks back to the library via ADE and then deleted them manually from my kobo ereader. I then reinstalled ADE and then had it opened and then I turned on my kobo ereader and then plugged into my computer. It then came up with the popup to authorise my kobo which I did and it works! I have successfully downloaded an ebook from the public library and because of the firmware upgrade I can now resize the font as well. Yay!
Perhaps I needed to authorise my kobo ereader first before I transferred an ebook from ADE to the ereader solved the problem?