I formatted an epub for an indie author. The author tells me that the cover displays properly on the Kindle and the Nook; I checked it in ADE and Calibre. It passed the IDPF epub validator. However, it is not displaying properly in the Kobo app on the author's iPad. There is a blank page after the cover. I consulted a colleague, who checked some of her covers in the Kobo app. Two covers of the same size, with the same svg coding—one had the blank page and one didn't.
My colleague suspects that the problem covers are being displayed on two pages, with a hairline of color on the top of the blank page. Is the app setting margins that bump the cover down? She tried inserting code to set margins to 0 and that didn't work.
Does anyone have any ideas as to the source of the problem and how to fix it?
I should perhaps add that I work in Oxygen XML editor, which does not like the code for the cover page. It flags it as invalid. All the other files are fine.
However the cover page passes the IDPF validator and displays properly (in most cases :) ).
I tried posting my cover page code here, but it did not display; I could not figure out how to escape it. If anyone can tell me how to escape the code, I can post it and y'all can pick it apart. (Yeah, I'm a duffer coder; it's been a long time since I took programming classes.)