PDF/X1 and Font Subset issue

I was uploading a PDF X-1 file of 164 page book to Kindle Direct Publishing. The file uploaded successfully but failed in the preview.

Then I remembered that Ernie had said do not use the font subset option.

I recreated the PDF X1 file with this option not selected and everything sailed though in minutes.

PLEASE fix this issue.

So did you outline the fonts?

No, the entire font rather than the individual characters used, was embedded. And I checked the properties of the PDF document in Acrobat to make sure all fonts were embedded.

Lovely