Files won't import to Calibre properly
Let me start my saying I'm very bad with computers, I find them vexing most of the time. A friend set up Calibre for me and it has always worked, not today.
So I was given a Kindle book for Christmas. I downloaded it onto my Mac. It opens on the Mac just fine in Kindle for Mac. I then click add books in Calibre and find the file which is a .azw file in the Kindle folder and Calibre says it's adding the book, it shows up on the list of titles. Then when I click on the book and try to open it, I get the Error message : Error could not open book Invalid start byte
If I try to put the book onto my Kindle that doesn't work either. When I click send to device I get a box that says, No suitable formats and asks if I want to auto convert that doesn't work either.
I did have a book that was in .pdf format that did import into calibre just fine last week and went onto my kindle with no problem today.
The only difference I see is that in the Calibre folder where the books are they are usually in .mobi file format and this book is in the .azw3 file format, I don't know if this has anything to do with my problem.
Any help would be greatly appreciated.