Hi all.
I imported my library in full in Calibre to correct metadatas, add covers, etc, saved everything on the disk and got for each ebook 3 files (epub, opf, jpg).
My concern is that when I want to import these files generated by Calibre itself on another computer, allways in Calibre, for an unknown reason, a fair amount of opf files are not saved in the folders of the new library

Hence, trying to send these books to my current device causes the error stated in the title ... Obviously, would you say, as it's indeed missing ...
But, do you see any reason why some are saved and other ones not (I modified all of them) ?
And is there a way to automatically generate the missing opf files ?
Many thanks for your help.
Regards