I published a children's book a few days ago and it was available on e-ink devices for a few days. For some reason this changed yesterday and it is no longer available on e-ink devices. Does anyone know why this would have happened and how I can make it available?
You can't. Fixed format can't be displayed on all devices. On your sales page is a list of devices. Additionally, on some devices with small screens, such as phones, fixed format books are almost unreadable. The disadvantages of fixed format always have to be weighed against the advantages.