I successfully made a landscape FXL for Kindle but now a portrait format won't finish the processing at KDP. It validates, it checks out in Oxygen Author, no errors of any kind! It works on devices when side loaded. It's mostly images and little text. I made it at 1200x1920 for a Fire 8.9 screen. Could this be where the trouble lies? I upload it fine and then before the processing finishes it gives me a warning that it failed to process. I al stumped. I can usually figure out these problems but not this time.