Problem signing into Amazon.com, can you help, please?

I have an account on Amazon.com and have made about 8 purchases using that account over several years. I live in NZ but my brother lives in the US so it is very handy for things like Christmas presents.

I’m trying to sign in to my account and it keeps telling me my password is wrong. Okay, I click “lost my password” and register a new password. Problem solved I thought, but no, the password is still incorrect. I thought I would cancel the account and start again but I see no way of doing that. I am tearing my hair out, can you help, please…