iBooks publish failure - Supported Language Problems?

I created some beautiful books in iBooks Author in the Khmer language - and have a line up of others waiting to be done.

I think that I have done everything right - and researched each step along the way. I established relationship with Apple to Produce successfully. Downloaded Producer have completed accurately the itmsp file for this book title. Filled out everything in iTunes producer - went to Deliver - and the response I get back is as below. It would appear that I can't submit this in ibooks format because of the language (assuming km = khmer).

It seems strange that everything is supported up to this point. OSX has Khmer native, I can create great books in iBooks Author, preview is perfect on iPad, iPad mini. I can select "Central Khmer" as the language of the book in Producer. Am I really being told that I need to modify my iBooks somehow to become epub 3 format in order to submit successfully to the the iBooks store? It seem counter-intuitive.

Please help, anybody! Thanks

Jacob

x Apple's web service operation was not successful

x Unable to authenticate the package: Golden_Book_Khmber.itmsp

x ERROR ITMS-6014: "Golden_Book_Khmer.ibooks: Language km for type main is only supported in epub 3 content." at Book (MZltmspBookPackage)

x ERROR ITMS-6014: "Golden_Book_Khmer_Sample.ibooks: Language km for type main is only supported in epub 3 content." at Book (MZltmspBookPackage)