Found answer. You have to add at the end of your password the 6 digits code you'll receive in another apple device. Here it is correctly explained -> https://developer.apple.com/forums/thread/117451?answerId=716214022#716214022

Hi. I found the solution: Go to App store and log in with your credentials. Then App store will say the user is not found and i'll ask you to write your password again. DON'T DO ANYTHING. In your iphone, ipad or other mac you will receive a notification saying you're trying to log in and it will give you a 6 digits code. In app store write again your password but at the end of the password add the 6 digits that you received in your iphone, ipad or mac. (ALL TOGETHER! Without a blank space between the password and the 6 digits code) Then press the button to log in, and it'll work :D (It is because of the legacy OS X there is no separate text box for the verification code.)