Amazon restricts book details that can be changed, after a book is published. And this includes your author name.
The scenario I am describing here is if you have misspelled your author name in Author Central, and you need to fix it to match the correct author name as printed on your book(s).
Unfortunately, it’s not possible to change the author name via KDP, and neither directly in Author Central. However, it is possible to contact Amazon via Author Central to request that they change your author name in Author Central.
1. First, log in to Author Central:
UK: https://author.amazon.co.uk/
US: https://author.amazon.com/
2. Next, click on the relevant ‘contact’ link depending on whether you are using Author Central in the UK or US:
UK: https://author.amazon.co.uk/en_US/contact?topicId=GRH7EU3PEDUHPPB4&subtopicId=GZZ37M6ELTGBJRCL
US: https://author.amazon.com/en_US/contact?topicId=GRH7EU3PEDUHPPB4&subtopicId=GZZ37M6ELTGBJRCL
Amazon has this message on that page (bold emphasis is mine):
To make Author Pages simple and easy for customers, we require that the name of the Author Page matches the author name listed for your books. We’re happy to correct Author Page names for typos or for consistency with author listings on your books; however, we can’t change the author name on your book’s detail page.
Use the ‘Contact Us’ button on the page linked above. You have a choice to send a message or – in working hours – to speak to an Amazon representative on the phone. Tell them you’ve mistyped your name in Author Central and that the correct spelling is on the book cover.
If this helps, please let us know in the comments.
PS Amazon has a breakdown of which book details can be changed via KDP after publishing.