Different cover on Books between MacOS and iOS

I recently imported some EPUB books into Books.app on my iMac, and they appear fine there. But on my iPad and iPhone, instead of the having the actual cover of the book, they have one of the "genercic" books covers provided by Apple. Page one of the book still has the original cover, but in the library view they show the generic cover.

Any thoughts on why this might be happening and how to fix. It makes it harder to choose the correct book without it's proper cover.

I'm on Catalina and iOS13

Thanks