Please go to the Microsoft website and insure any stored payment information is up to date and not using an expired payment method (even if you're not using it to pay for the subscription itself). If you've done that, please clear your console cache by turning it off, unplugging it for 30-60 seconds, then plugging it back in and trying. If that doesn't work, you'll need to contact Microsoft. Destiny 2's matchmaking and multiplayer system uses the console's Multiplayer requirement, and the console is reporting to the game that you don't have Xbox Live Gold, which means it won't let you take part in anything that requires it.