Q: iTunes Producer to iBooks

I'm really hoping someone can help me with this.

I'm trying to upload my ebook to iTunes connect so that I can put it for sale. I have uploaded the ePub document to iTunes producer but when I try to submit so that it can publish on my iTunes connect, it says that the file is too large. This is not a massive book, and I can't figure out why it isn't going through.

Apple does not have any chat support and I live abroad so calling support is really expensive. They don't even have an email where I can reach out for help.

I'm super frustrated. Can anyone help me or should I just bag publishing on iBooks and focus on Kindle and Kobo which appear to be more user-friendly?