Comment 1 for bug 1836294

There is a windows specific issue in calibre 3.45.0 causing this error. I am
in the process of tracking it down, when I do I will make a new calibre release.
In the meantime I suggest downgrading to 3.44.0, which you can get from here:
https://download.calibre-ebook.com/3.44.0/

 status fixreleased