Publish an external epub file

bozenaK wrote:

I need to publish to the iBook store my epub book created on Indesign.

You may be able to do this using iTunes producer

https://itunespartner.apple.com/books/tools

or the publishing portal

https://authors.apple.com/publish-your-book

Pages won't open an ePUB regardless of its source. You are dealing with the Apple Book ecosystem, and there is no Apple interest or compatibility with admitting other ePUBs generated outside of Apple's tools. As it turns out, Apple injects some Apple-specific CSS3 styles into ePUBs generated by Pages, or iBooks Author, and InDesign does not.

The Apple Book Store revolves around creating ePUB with Apple's tools. I doubt you can get an ePUB into the store that originated in InDesign.