KDP Login: How to Sign In to Amazon KDP, and Fix It When It Won't Let You In
Short answer: go to kdp.amazon.com, click Sign in, and use the email address or mobile number of the Amazon account you publish under. UK authors use the same site: typing kdp.amazon.co.uk takes you straight to kdp.amazon.com. There is no separate KDP password; it is your Amazon login.
KDP Readiness Score Blog7 min read