Every Amazon Appstore developer’s account is linked to an Amazon.com (customer/shopping) account with same account e-mail id and password. If you update your credentials on Amazon.com, they will also be updated on developer.amazon.com.
If you’re having trouble signing into your developer account, here are some things to check:
Incorrect Email Address
Your email address must be in this format: username@domain.com (or .net, .org, .edu, etc.). If you have more than one email address, be sure that you’re using the correct email address and password combination for the account you are trying to access. If you use a different email address for the Developer Console and Amazon.com, and you’ve recently been shopping on Amazon.com, you may be logged into the wrong account.
Incorrect Password
If you’re sure you’re using the correct email address, try to reset your password. If you are unsuccessful in using the “Forgot Your Password” tool, please contact Amazon Customer Service team for Account & Login issues. Please note that Amazon Developer Support is unable to assist with password issues, and you will need to contact Amazon Customer Service.