I am using calibre, version 0.9.5 on the Mac, and am trying to convert a .docx file.
I have set the language to French in the metadata, but otherwise have changed nothing in that tab.
On clicking "Convert Books", I get the following error message:
"WARNING: Could not convert some books: Could not convert 1 of 1 books, because no suitable source format was found."
Calibre seems to recognize that it is a .docx file, as it displays this in the section of the main screen under the book cover.
I want to convert to MOBI, but this error occurs before I designate the output format.
If I first save the .docx file as PDF, it converts with no problem. I understand the result will have fewer annoyances if I start with a .docx file, so I would prefer to do so.