Hi
I'm having the same problem as below with uploading to Ingramspark
https://www.mobileread.com/forums/sh...d.php?t=282146
I get the errors
[ERROR]content.opf: 1,133: URL expected instead of calibre:
[ERROR]content.opf: 40,41: Undecleared prefix: calibre
[ERROR]content.opf: 41,50: Undecleared prefix: calibre
But when I edit and go into content.opf (Right Click, Edit Book) and remove the references as the previous post indicated, save and export and epub3 file I get the same errors. I go back into content.opf and they're back! It's driving me mad and I know it's going to be user error!