As of July 29, 2024 the storefront shut down.
xboxera.com
The Xbox 360 Store Will Close July 2024, But You Can Keep Playing Your Favorite Games
news.xbox.com
As I find more on this, I will update this topic.
The Xbox 360's Marketplace is Now Permanently Closed
As Microsoft stated back in August of last year, the Xbox 360's Marketplace has been shuttered as of today, the 29th of July. Players who boot up an Xbox
xboxera.com
The Xbox 360 Store Will Close July 2024, But You Can Keep Playing Your Favorite Games
The Xbox 360 Store Will Close July 2024, But You Can Keep Playing Your Favorite Games - Xbox Wire
On July 29, 2024, Xbox will stop supporting the ability to purchase new games, DLC, and other entertainment content from the Xbox 360 Store on the console and the Xbox 360 Marketplace. This change will not affect your ability to play Xbox 360 games or DLC you have already purchased.
news.xbox.com
As I find more on this, I will update this topic.