NBA 2K18's servers will be spinning down January 18th, 2020.
Accordingly, any mode in NBA 2K18 that earns or uses VC will be affected, along with any other online function (such as the MyTEAM mode and online matches against other players). However, you can still play offline quick games, as well as the MyGM and MyCAREER modes offline. This will let you earn SP rather than VC.
If you created a MyCAREER or MyGM online save file before this, the server shutdown means the data will no longer be available for use and you’ll have to start a new game in those modes.