NBA 2K15, NBA 2K14, and NBA 2K13 servers will be down on July 8th at 3 AM PT / 6 AM ET for server maintenance. The 2K Support Twitter account will give an update when it has been completed. This will impact my2K accounts and online features connected to the service.
— 2K Support (@2KSupport) July 8, 2015
[UPDATE] Within the last hour, NBA 2K15 PS4/XB1 servers are back on. Online features are now working.
Via 2K Support