If you have been encountering a "This Feature is Unavailable" message in NBA 2K21, 2K Sports has released an article on how to fix this error message. 2K Chad of 2K Support updated an article in December 2020 discussing this issue, and introduced the possibilities for these issues, and offered fixes for both Xbox and PlayStation.
If you have a stable internet connection on every other game and are an Xbox Live Gold member, then the problem may be with restrictions that keep you from connecting, according to 2K.
1.Press the Xbox button to return to the Home screen.
2.Scroll left from Home to open the guide.
3.Select "Settings". Then head to "Account."
4.From there, select "Privacy and online safety" and head to "View details and customize".
5.The following needs to be set to "Allow"/"Everybody": "Share content using Kinect”, "Others can communicate with voice", and "You can see and share content."
6.Then, clear your cache.
If this isn't the problem, 2k says you may have more than one account logged into your Xbox. To fix this, simply log out of the profile you don't wish to use on NBA 2K by using the Xbox button, scrolling to Profile and System, and clicking "sign out."
If problems continue to persist, head over to Xbox Support for more troubleshooting. For PlayStation players, the problem may be an account with child restrictions may be signed in and prohibiting you from playing NBA 2K21 online. To sign out of this account:
1.Hold down the PlayStation button on your controller.
Select Power > Switch User
2.You'll see a list of accounts on your PlayStation 4, with notes on which accounts are logged in. Select any account that is logged in but isn't the account you're trying to use.
3.At the home screen of that account, hold down the PlayStation button and select Power > Log Out of PS4.
4.Repeat as necessary until only the adult account you want to use is still logged in.