"Incorrect email/password combination"[1]
This is despite being logged in to FB with the same password.
The fix is to change your password, log out and log back in with the changed password. You will then be able to delete your account without issue.
Maybe the author could add this information to their post?
People have been asking on the FB help forum for years about how to resolve this error. FB refuses to answer anyone asking for help with this error. I'm guessing their failure to mention this or address this is quite intentional.
Oh and the audio versions of the CAPTCHAs are all completely unintelligible gibberish. I'm guessing this is intentional as well.
[1] https://www.facebook.com/help/community/question/?id=4018056...