[KDP REJECTION] Why Did KDP Reject my Book For Not Having Enough Pages with Text on the Spine?

KDP may reject your book and say something about you do not have enough pages to have text on your spine.

KDP says this about Text on the Spine: Spine text. Your book must have at least 79 pages to add spine text. If your book has fewer than 79 pages, don’t add spine text. Also, spine text needs at least 0.0625" (1.6 mm) on either side so the text doesn't wrap onto the front or back cover. Source.

So you will have to add more pages to get to their minimum or just remove the text off the spine.