People search KDP Bookshelf, Amazon KDP Bookshelf, and Kindle Direct Publishing bookshelf when they mean Amazon’s dashboard. That is not the AuthorShelf author portal login.
What KDP Bookshelf is
Amazon’s list of titles you published through KDP: Kindle files, paperbacks, pricing, and Amazon reports. You sign in at Amazon, not at AuthorShelf.
What the AuthorShelf Portal is
A lifetime production command center on every package: six phases, file versions, eProof and cover approvals, team messages, then royalties after Title Live. Sign-in help: Author Portal login. Features: Author Portal features.
When you use both
If you DIY KDP, you live on the Bookshelf. If you buy an AuthorShelf package, production happens in our portal; Amazon still has a retailer account for the live listing. We do not replace KDP. We produce files and coordinate setup so you are not lost in two specs at once. See IngramSpark vs KDP.