Originally Posted by kovidgoyal
SONY readers are among the les srobust set of EPUB readers in terms of what markup trips them up. I suggest converting the file to MOBI and then converting the MOBI to epub, that will dumb down the markup enough that the SONY should handle it. You may lose some formatting that MOBI cannot handle, however.
This worked: converting ePub->MOBI->ePub gave an ePub that I was able to open in the PRS-T1.