I cannot create an Apple ID username or manage my Apple ID account

Question

Hi!
I'm lucky to be able to ask these questions at all: I'm using my father's apple ID at the moment. I tried to ask a question (concerning another problem I'm having) using my own account, but I get stuck in some sort of strange loop: I have to choose a 'username' in order to be able to use the support communities. I enter the username I would like, click 'continue', but then I get the warning: 'an account utilizing this email address already exists. Only one account per email address is allowed on Apple Support Communities.' Yet, I didn't try to create a new account using an email address that is already linked to another account, I merely wanted to choose a username to go along with my existing apple ID. (As a said, I am now using my father's apple ID and the username he made just now while we are trying to figure out what is going wrong and hoping to see whether he would experience the same problems.)
So, upon receiving this warning I go to 'My Apple ID' at the bottom of the screen, I fill in my password, and the screen I'm sent to is again the one where I can create my username. My father doing the same thing on the other hand - he was able to create a username just fine - upon entering his password, is sent to the correct screen where he can edit and manage his personal information (like change his password or the password security questions.)
So basically, I am not able to create a username connected to my own Apple ID, and I cannot even enter the screen where I can manage my Apple ID account. (This is true for both Safari and Firefox (I'm using the latter at the moment).)
It might be an important piece of information that this problem (of not being able to choose a username, not being able to access the communities, and not being able to alter my apple ID) is only my problem and not my dad’s. I can do all those things just fine with his account. Whether it is in Firefox or in Safari.
What could be the problem here?
Help would be very much appreciated!

Answer 1

According to Create an AppleID:
Choose an Apple ID and password.
Enter your primary email address as your Apple ID. This will be used as the contact email address for your account. Please note that this email address must be verified before you can use certain Apple services.
And, unless I'm missing something, it appears that you're trying to use your father's e-mail address. Start at Find your AppleID and see if you can resolve the issue.