For about a year now I have successfully downloaded books from the library, loaded onto the Adobe Digital Software and then moved it to my Kobo. All of a sudden, it stopped working. When I transfer the book to the ereader (from adobe software) it says the book is there. However, it is not there. I have tried 4 different books now, all the same result. Should I delete my Adobe software and start new?
It sounds more as if there is some corruption on the eReader.
Back up any books that you only have on the Kobo first.
Then try a factory reset: your kobo instructions should be able to tell you how.
You will then probably need to re-register the Kobo with your AdobeID using ADE.