@petzi:
You are still doing it incorrectly. Follow the advice in my prior post about creating a fresh Calibre Zotero Library and using
only ZMI to add the missing books from Zotero itself.
Please read this post again:
https://www.mobileread.com/forums/sho...5&postcount=20
Abandon your current Calibre Library and start over with a brand new created freshly by Calibre via the menu option for that. Only ZMI can import your Zotero books,
not you via "Add Books".
DaltonST
DaltonST