When I was choosing an GamerTag, my own GamerTag didn't set, but generated set.

Hi Try chage by this page https://social.xbox.com/en-us/changegamertag (This page you can change for Free and was give by the support one time

Hi, sorry you are having issues. If I read this correctly it didnt give you the gamertag you wanted but gave you an auto generated one instead. This means you still have a free gamertag change left. As you always get one free if you have an autogenerated
one at the start.

When you first setup your profile way back in the day the system automatically generated a gamertag for you. If you did not choose that option and put your own gamertag in then that counts as your free gamertag change

When creating an account for the first time, it will assign an automatic random generated gamertag. If you choose a different one, whether from the suggested list or typing your own in, then that is classed as your free gamertag change.

First I Sign In with my profile. Then I go to settings and pick "Join Xbox Live". Then the Welcome to Xbox Live box comes up and says: Set up a Microsoft account for Xbox Live; Get your unique gamertag; Choose your membership level. Then it asks for my name;
email; & password. Then it says "Email or Password Not Valid" Can't sign in, the email address or password didn't work. Try a different one, or use your app password to sign in to: Just so you know I am not using a Microsoft email account(because any one of
those generates its own gamertag) I am using my road runner email account.