I have tried to upload an epub file generated by Sigil on Google Books Partner Center and I get the following error message (excerpt):
I have found a similar question on StackExchange and wasnt able to figure out the solution there.
Code:
Required: Fix ePub and resubmit
The ePub you submitted has the following errors. These will prevent the book from going live. See the Help Center for more information. Please correct and resubmit.
index_split_003.html:55, 248: Error while parsing file: attribute "role" not allowed here; expected attribute "accesskey", "charset", "coords", "dir", "hreflang", "lang", "rel", "rev", "shape", "style", "tabindex", "target", "type" or "xml:lang"
...
index_split_009.html:175, 288: Error while parsing file: attribute "data-docx-vert" not allowed here; expected attribute "accesskey", "charset", "class", "coords", "dir", "href", "hreflang", "id", "lang", "rel", "rev", "shape", "style", "tabindex", "target", "title", "type" or "xml:lang"
