We've created this Forum Thread with some workarounds and advice to assist you in publishing you ebook.
Created epub 3.0 in Calibre - trouble importing
Hello! I apologize if someone has already asked this question - I couldn't find a search function in the forum.
I created an epub in Calibre which validates as 3.0.1 at validator.idpf.org. However, when I try to import it to Lulu, the error document says it's validating against version 2.0, and the subsequent list of errors is consistent with that.
Does Lulu not support epub 3.0? What are my options at this point? Thank you in advance.