Compiling to 6 by 9

I spent hundreds of hours formatting my 6 by 9 book for compile and today when I went to correct some typos, it is compiling to US Letter instead of 6 by 9 and I don’t have the 6by 9 option available anymore. I sent the file to my editor, Anne Rainbow and she was able to compile it using my saved formatting but I still am not able to.

What happened and how do I get my book formatting back? My book launch is on the 11th May and at this rate I wont have any printed copies available for purchase.

The Paperback 6x9 Compile format is set to that size, but there is an option if to edit the Page Setup on the Page Settings tab of the compile format editor.