I contacted Apple and they get back with the following email. I tried what they suggested And on the first try It successfully got imported. Let me explain What I was doing wrong. I had an image name cover.jpg inside /OEBPS/images folder, with the dimension of 1400 X 2080. And I was using the same image in the iTunes Producer's Asset tab. Since my image was perfectly ok with iTunes Producer but inside /OEBPS/images it ended in error because it exceeded the 2 million pixels limit. ( 1400X 2080 = 2,912,000 ).
So What I did I resized the image inside the /OEBPS/images folder and reduced it to 1077 X 1600 which is under 2 million pixels.
What I figured out is that the image inside the epub file is used for the cover of the book inside iBookStore. And the image that we provide in iTunes Producer is used as a marketing image.
I am happy that finally I was able to upload it. Please let me know if I am not clear enough to convey what I am trying to.
The delivery of your book with Vendor ID 9781625908735 ultimately ended in error because the EPUB file you submitted contains an interior image(s) that exceeds 2 million pixels. You should have received an email from us detailing which image(s) are causing this import error. If you did not receive this notice, make sure to opt in to Content Ticket notifications in iTunes Connect. You may do so in the Manage Users module then selecting the Notifications tab. It appears the image that is causing this error is /OEBPS/images/cover.jpg.
The 2 million pixel limit only applies to images inside the EPUB file. You may calculate whether an image inside the EPUB file exceeds 2 million pixels by multiplying the height of the image with the width. EPUB files with images exceeding 2 million pixels will not go live on the iBookstore. It is important that you modify the image size dimensions in the program you used to create your book and save the changes before you export the updated book as an EPUB.
Note that the book's cover art that appears on the iBookstore, which is delivered separately as an asset in addition to your EPUB file in iTunes Producer, is not subject to the 2 million pixel limit. The book's cover art must be at least 1400 pixels along the shorter axis, must use RGB color mode, and must use the .png or .jpg format.
Once you have ensured that each image inside your EPUB file does not exceed 2 million pixels, make sure all required metadata fields are filled out in iTunes Producer, upload the updated EPUB file in the Assets tab then click on Deliver when you are ready to deliver your book to us.
For more information on building EPUBs for the iBookstore, download the iBookstore Asset Guide from the Deliver Your Content module in iTunes Connect. If you have any further questions regarding this 2 million pixel limit, please reply to this email. For all other inquiries, fill out a Contact Us form in iTunes Connect, referencing the follow up number 247923787 for your case.